“Failed to save event” when adding new attendee to a recurring event

[kkrasoo]

Steps to reproduce

1. Create a new recurring event (e.g., weekly or daily).
2. Save it successfully.
3. Reopen the event and add a new participant (attendee).
4. Try to save the event.

Expected behavior

The recurring event should update successfully and include the newly added participant(s).

Actual behavior

The system displays an error:

“Failed to save event”

and the change is not applied.

Calendar app version

5.3.7

CalDAV-clients used

no

Browser

Firefox 130

Client operating system

Windows 10

Server operating system

Linux 6.1.0-35-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.137-1 (2025-05-07) x86_64

Web server

None

Database engine version

MySQL

PHP engine version

PHP 8.3

Nextcloud version

30.0.13 - 30.0.13.1

Updated from an older installed version or fresh install

None

List of activated apps

Nextcloud configuration

Web server error log

Log file

Browser log

Additional info

This issue affects all users in our organization who manage recurring meetings.
Currently, the only workaround is to delete the recurring event and recreate it whenever the attendee list changes.
This is time-consuming, especially when many participants are involved.

Could you please confirm whether this issue is already known, and if a fix or workaround is planned for an upcoming release?

[SebastianKrupinski]

Hi @kkrasoo

Are there any relevant errors in the browser console or nextcloud.log?

[kkrasoo]

PUT

XHRPUT
https://drive.rarus.ru/remote.php/dav/calendars/MIROSS/personal/4050F774-CCB2-4663-9FF8-BBCEEF83A4DA.ics
[HTTP/2 412 99ms]

PUT
https://drive.rarus.ru/remote.php/dav/calendars/MIROSS/personal/4050F774-CCB2-4663-9FF8-BBCEEF83A4DA.ics
Состояние
412
ВерсияHTTP/2
Передано728 б (размер 308 б)
Referrer policyno-referrer-when-downgrade
Приоритет запросаHighest
Поиск в DNSСистема

[ERROR] calendar: Failed to save event: Error
Object { app: "calendar", uid: "MIROSS", level: 1, error: Error }
calendar-main.js:2:2697092
log index.mjs:54
error index.mjs:72
save EditorMixin.js:499
saveAndLeave EditorMixin.js:518
saveEvent EditFull.vue:682
prepareAccessForAttachments EditFull.vue:676
future EditFull.vue:1
VueJS 4
saveThisAndAllFuture SaveButtons.vue:113
VueJS 4
click NcButton-CWPBzbcC.mjs:284
VueJS 33
WEEKLY calendar-main.js:2:5621310
Uncaught (in promise) Error:
y index.mjs:589
C index.mjs:595
request index.mjs:851
put index.mjs:673
update index.mjs:1193
updateCalendarObject calendarObjects.js:108
r pinia.mjs:1399
saveCalendarObjectInstance calendarObjectInstance.js:1485
r pinia.mjs:1399
save EditorMixin.js:494
saveAndLeave EditorMixin.js:518
saveEvent EditFull.vue:682
prepareAccessForAttachments EditFull.vue:676
future EditFull.vue:1
VueJS 4
saveThisAndAllFuture SaveButtons.vue:113
VueJS 4
click NcButton-CWPBzbcC.mjs:284
VueJS 33
calendar-main.js:2:2405905

and maybe it's

"content": {
"mimeType": "application/xml; charset=utf-8",
"size": 308,
"text": "\n<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">\n <s:exception>Sabre\DAV\Exception\PreconditionFailed</s:exception>\n <s:message>An If-Match header was specified, but none of the specified ETags matched.</s:message>\n <s:header>If-Match</s:header>\n</d:error>\n"
},

[SebastianKrupinski]

Morning,

Yes this caused the errors,

<d:error xmlns:d="DAV:" xmlns:s="[http://sabredav.org/ns">\n](http://sabredav.org/ns/%22%3E/n) <s:exception>Sabre\DAV\Exception\PreconditionFailed</s:exception>\n <s:message>An If-Match header was specified, but none of the specified ETags matched.</s:message>\n <s:header>If-Match</s:header>\n</d:error>

But question is why? I see that your system is still running an old version of Calendar, the current one is v5.5. And the current server version is NC 30.0.17. Try upgrading. That said for community issues we are currently supporting NC31+, so I would recommend upgrading to 31.

[kkrasoo]

Hi!
The issue is reproduced in exactly the same way on the latest versions.

NC 31.0.10 and Calendar: 5.5.8

14:53:34.708 XHRPUT
https://nctest4.rarus.ru/remote.php/dav/calendars/admin/personal/3AA79818-9561-48B6-BEB8-309A47558B5B.ics
[HTTP/2 500 71ms]

14:56:17.861 XHRPUT
https://nctest4.rarus.ru/remote.php/dav/calendars/admin/personal/3AA79818-9561-48B6-BEB8-309A47558B5B.ics
[HTTP/2 500 85ms]

<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
<s:exception>Error</s:exception>
<s:message>__clone method called on non-object</s:message>
</d:error>

[squatica]

I'm also getting "Failed to save event" when removing a participant from a recurring event. The caldav error is different though:

<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
  <s:exception>TypeError</s:exception>
  <s:message>A type error occurred. For more details, please refer to the logs, which provide additional context about the type error.</s:message>
</d:error>

Unfortunately I can't access the logs, this is on Hetzner hosted Nextcloud.
Also it's not every recurring event that does this - I was able to edit two other events, and only the third one failed to save. But strangely, the participants were the same.

One more thing I noticed: when I export the failed event to .ics, it contains two VEVENT objects, same UID, the first has SEQUENCE:0, DTSTART a month ago and the old list of attendees, the second has SEQUENCE:1, DTSTART of the day I wanted to modify and the new list of attendees. But Nextcloud only shows the old list of attendees. This feels like modifying the list of attendees is wrongly creating two VEVENTS, instead of splitting the sequence, because I also see a bunch of RELATED-TO;RELTYPE=SIBLING from the previous modifications.

[SebastianKrupinski]

The two VEVENT's are probably correct depending on the modification action.

Can you post the event, please. Strip out any personal information like email addresses, but leave the reset as is please

[SebastianKrupinski]

@kkrasoo that error looks familiar

Try this patch,

nextcloud/server#52882

If it works, I will back port it

[The-1ST]

this recurring events are killing me I am experiencing issues like this with recurring events too some time It does not shows attendees to other attendees some time I can not delete. some time I can not update and so more. some time It gets duplicated for attendees and so more .

[SebastianKrupinski]

@The-1ST

Can you provide us some more information? Like a browser console log error or nextcloud log error?

[RegisPerdreau]

I propose to test add/remove attendees, the error occurs when remove attendees too.