diff --git a/lib/ExportDestination.php b/lib/ExportDestination.php
index 8a0774ce..051b5297 100644
--- a/lib/ExportDestination.php
+++ b/lib/ExportDestination.php
@@ -56,26 +56,24 @@ public function __construct($r) {
 	/**
 	 * {@inheritDoc}
 	 */
-	public function addFileContents(string $path, string $content): bool {
+	public function addFileContents(string $path, string $content): void {
 		$stream = fopen('php://temp', 'r+');
 		fwrite($stream, $content);
 		rewind($stream);
 		$this->streamer->addFileFromStream($stream, $path);
-		return true;
 	}
 
 	/**
 	 * {@inheritDoc}
 	 */
-	public function addFileAsStream(string $path, $stream): bool {
+	public function addFileAsStream(string $path, $stream): void {
 		$this->streamer->addFileFromStream($stream, $path);
-		return true;
 	}
 
 	/**
 	 * {@inheritDoc}
 	 */
-	public function copyFolder(Folder $folder, string $destinationPath): bool {
+	public function copyFolder(Folder $folder, string $destinationPath): void {
 		$this->streamer->addEmptyDir($destinationPath, [
 			'timestamp' => $folder->getMTime(),
 		]);
@@ -92,22 +90,19 @@ public function copyFolder(Folder $folder, string $destinationPath): bool {
 					'timestamp' => $node->getMTime(),
 				]);
 			} elseif ($node instanceof Folder) {
-				$success = $this->copyFolder($node, $destinationPath.'/'.$node->getName());
-				if ($success === false) {
-					return false;
-				}
+				$this->copyFolder($node, $destinationPath.'/'.$node->getName());
 			} else {
-				return false;
+				// ignore unknown node type, shouldn't happen
+				continue;
 			}
 		}
-		return true;
 	}
 
 	/**
 	 * {@inheritDoc}
 	 */
-	public function setMigratorVersions(array $versions): bool {
-		return $this->addFileContents("migrator_versions.json", json_encode($versions));
+	public function setMigratorVersions(array $versions): void {
+		$this->addFileContents("migrator_versions.json", json_encode($versions));
 	}
 
 	/**
diff --git a/lib/ImportSource.php b/lib/ImportSource.php
index 0fb44550..5b047744 100644
--- a/lib/ImportSource.php
+++ b/lib/ImportSource.php
@@ -90,7 +90,7 @@ public function pathExists(string $path): bool {
 	/**
 	 * {@inheritDoc}
 	 */
-	public function copyToFolder(Folder $destination, string $sourcePath): bool {
+	public function copyToFolder(Folder $destination, string $sourcePath): void {
 		// TODO log errors to ease debugging
 		$sourcePath = rtrim($sourcePath, '/').'/';
 		$files = $this->archive->getFolder($sourcePath);
@@ -99,9 +99,7 @@ public function copyToFolder(Folder $destination, string $sourcePath): bool {
 			foreach ($files as $path) {
 				$stat = $this->archive->getStat($sourcePath . $path);
 				if ($stat === null) {
-					// TODO: use exception
-					echo "Stat information not found for " . $sourcePath . $path . "\n";
-					return false;
+					throw new UserMigrationException("Failed to get stat information from archive for " . $sourcePath . $path . "\"");
 				}
 				if (str_ends_with($path, '/')) {
 					try {
@@ -113,16 +111,12 @@ public function copyToFolder(Folder $destination, string $sourcePath): bool {
 					} catch (NotFoundException $e) {
 						$folder = $destination->newFolder($path);
 					}
-					if ($this->copyToFolder($folder, $sourcePath.$path) === false) {
-						// TODO: use exception
-						echo "copy to $sourcePath.$path failed\n";
-						return false;
-					}
+					$this->copyToFolder($folder, $sourcePath.$path);
 					$folder->touch($stat['mtime']);
 				} else {
 					$stream = $this->archive->getStream($sourcePath.$path, 'r');
 					if ($stream === false) {
-						return false;
+						throw new UserMigrationException("Failed to get " . $sourcePath . $path . " from archive\"");
 					}
 					try {
 						$file = $destination->get($path);
@@ -139,9 +133,8 @@ public function copyToFolder(Folder $destination, string $sourcePath): bool {
 				}
 			}
 		} catch (NotPermittedException $e) {
-			return false;
+			throw new UserMigrationException("Could not import files due to permission issue", 0, $e);
 		}
-		return true;
 	}
 
 	/**
diff --git a/lib/Migrator/FilesMigrator.php b/lib/Migrator/FilesMigrator.php
index 61df862c..1044fccc 100644
--- a/lib/Migrator/FilesMigrator.php
+++ b/lib/Migrator/FilesMigrator.php
@@ -99,15 +99,19 @@ public function export(
 		$uid = $user->getUID();
 		$userFolder = $this->root->getUserFolder($uid);
 
-		if ($exportDestination->copyFolder($userFolder, static::PATH_FILES) === false) {
-			throw new UserMigrationException("Could not export files.");
+		try {
+			$exportDestination->copyFolder($userFolder, static::PATH_FILES);
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export files.", 0, $e);
 		}
 
 		try {
 			$versionsFolder = $this->root->get('/'.$uid.'/'.FilesVersionsStorage::VERSIONS_ROOT);
 			$output->writeln("Exporting file versions…");
-			if ($exportDestination->copyFolder($versionsFolder, static::PATH_VERSIONS) === false) {
-				throw new UserMigrationException("Could not export files versions.");
+			try {
+				$exportDestination->copyFolder($versionsFolder, static::PATH_VERSIONS);
+			} catch (\Throwable $e) {
+				throw new UserMigrationException("Could not export files versions.", 0, $e);
 			}
 		} catch (NotFoundException $e) {
 			$output->writeln("No file versions to export…");
@@ -121,8 +125,10 @@ public function export(
 		$tagger = $this->tagManager->load(Application::APP_ID, [], false, $uid);
 		$tags = $tagger->getTagsForObjects(array_values($objectIds));
 		$taggedFiles = array_filter(array_map(fn ($id) => $tags[$id] ?? [], $objectIds));
-		if ($exportDestination->addFileContents(static::PATH_TAGS, json_encode($taggedFiles)) === false) {
-			throw new UserMigrationException("Could not export tagged files information.");
+		try {
+			$exportDestination->addFileContents(static::PATH_TAGS, json_encode($taggedFiles));
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export tagged files information.", 0, $e);
 		}
 
 		$output->writeln("Exporting file systemtags…");
@@ -136,8 +142,10 @@ public function export(
 			$systemTags
 		);
 		$systemTaggedFiles = array_filter(array_map(fn ($id) => $systemTags[$id] ?? [], $objectIds));
-		if ($exportDestination->addFileContents(static::PATH_SYSTEMTAGS, json_encode($systemTaggedFiles)) === false) {
-			throw new UserMigrationException("Could not export systemtagged files information.");
+		try {
+			$exportDestination->addFileContents(static::PATH_SYSTEMTAGS, json_encode($systemTaggedFiles));
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export systemtagged files information.", 0, $e);
 		}
 
 		$output->writeln("Exporting file comments…");
@@ -160,8 +168,10 @@ function (IComment $comment): array {
 				);
 			}
 		}
-		if ($exportDestination->addFileContents(static::PATH_COMMENTS, json_encode($comments)) === false) {
-			throw new UserMigrationException("Could not export file comments.");
+		try {
+			$exportDestination->addFileContents(static::PATH_COMMENTS, json_encode($comments));
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export file comments.", 0, $e);
 		}
 
 		// TODO other files metadata should be exported as well if relevant.
@@ -197,8 +207,10 @@ public function import(
 
 		$uid = $user->getUID();
 
-		if ($importSource->copyToFolder($this->root->getUserFolder($uid), static::PATH_FILES) === false) {
-			throw new UserMigrationException("Could not import files.");
+		try {
+			$importSource->copyToFolder($this->root->getUserFolder($uid), static::PATH_FILES);
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not import files.", 0, $e);
 		}
 
 		$userFolder = $this->root->getUserFolder($uid);
@@ -210,8 +222,10 @@ public function import(
 				$versionsFolder = $this->root->newFolder('/'.$uid.'/'.FilesVersionsStorage::VERSIONS_ROOT);
 			}
 			$output->writeln("Importing file versions…");
-			if ($importSource->copyToFolder($versionsFolder, static::PATH_VERSIONS) === false) {
-				throw new UserMigrationException("Could not import files versions.");
+			try {
+				$importSource->copyToFolder($versionsFolder, static::PATH_VERSIONS);
+			} catch (\Throwable $e) {
+				throw new UserMigrationException("Could not import files versions.", 0, $e);
 			}
 		} else {
 			$output->writeln("No file versions to import…");
diff --git a/lib/Service/UserMigrationService.php b/lib/Service/UserMigrationService.php
index 1106cc2a..f3b6c5f0 100644
--- a/lib/Service/UserMigrationService.php
+++ b/lib/Service/UserMigrationService.php
@@ -111,8 +111,10 @@ public function export(IExportDestination $exportDestination, IUser $user, ?arra
 			$migrator->export($user, $exportDestination, $output);
 			$migratorVersions[$migrator->getId()] = $migrator->getVersion();
 		}
-		if ($exportDestination->setMigratorVersions($migratorVersions) === false) {
-			throw new UserMigrationException("Could not export user information.");
+		try {
+			$exportDestination->setMigratorVersions($migratorVersions);
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export user information.", 0, $e);
 		}
 
 		$exportDestination->close();
@@ -169,8 +171,10 @@ protected function exportUserInformation(IUser $user,
 			'enabled' => $user->isEnabled(),
 		];
 
-		if ($exportDestination->addFileContents(IImportSource::PATH_USER, json_encode($userinfo)) === false) {
-			throw new UserMigrationException("Could not export user information.");
+		try {
+			$exportDestination->addFileContents(IImportSource::PATH_USER, json_encode($userinfo));
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export user information.", 0, $e);
 		}
 	}
 
@@ -214,8 +218,10 @@ protected function exportVersions(string $uid,
 			\OC_App::getAppVersions()
 		);
 
-		if ($exportDestination->addFileContents("versions.json", json_encode($versions)) === false) {
-			throw new UserMigrationException("Could not export versions.");
+		try {
+			$exportDestination->addFileContents("versions.json", json_encode($versions));
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export versions.", 0, $e);
 		}
 	}
 
@@ -229,8 +235,10 @@ protected function exportAppsSettings(string $uid,
 
 		$data = $this->config->getAllUserValues($uid);
 
-		if ($exportDestination->addFileContents("settings.json", json_encode($data)) === false) {
-			throw new UserMigrationException("Could not export settings.");
+		try {
+			$exportDestination->addFileContents("settings.json", json_encode($data));
+		} catch (\Throwable $e) {
+			throw new UserMigrationException("Could not export settings.", 0, $e);
 		}
 	}