# How should I ascertain whether an HTTP 400, that is reported by DAVx5, every time it polls a specific ICS file, is its fault, or \[the\] NextCloud \[provider\]'s?

**URL:** <https://help.nextcloud.com/t/how-should-i-ascertain-whether-an-http-400-that-is-reported-by-davx5-every-time-it-polls-a-specific-ics-file-is-its-fault-or-the-nextcloud-provider-s/233713>\
**Category:** ℹ️ Support\
**Tags:** davx5, nc30, cloudflare\
**Created:** [October 8, 2025, 3:32pm UTC](https://help.nextcloud.com/t/how-should-i-ascertain-whether-an-http-400-that-is-reported-by-davx5-every-time-it-polls-a-specific-ics-file-is-its-fault-or-the-nextcloud-provider-s/233713 "2025-10-08T15:32:09Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![rokejulianlockhart](https://help.nextcloud.com/user_avatar/help.nextcloud.com/rokejulianlockhart/32/77112_2.png) [@rokejulianlockhart](https://help.nextcloud.com/u/rokejulianlockhart)\
**Post date:** [October 8, 2025, 10:20pm UTC](https://help.nextcloud.com/t/how-should-i-ascertain-whether-an-http-400-that-is-reported-by-davx5-every-time-it-polls-a-specific-ics-file-is-its-fault-or-the-nextcloud-provider-s/233713/3 "2025-10-08T22:20:08Z")

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@jtr, thank you! That at least correlates this with:

1. 

> [@Error while updating birthday calendar: Calendar object with uid already exists in this calendar collection](https://help.nextcloud.com/t/error-while-updating-birthday-calendar-calendar-object-with-uid-already-exists-in-this-calendar-collection/75330/1):
>
> > Calendar object with uid already exists in this calendar collection.

2. 

> [@Error: Calendar object with uid already exists in this calendar collection](https://help.nextcloud.com/t/error-calendar-object-with-uid-already-exists-in-this-calendar-collection/45729/3):
>
> > Calendar object with uid already exists in this calendar collection.

3. [`bugs.kde.org/show_bug.cgi?id=406917#c0`](https://bugs.kde.org/show_bug.cgi?id=406917#c0:~:text=Calendar%20object%20with%20uid%20already%20exists%20in%20this%20calendar%20collection)

4. [`bugzilla.mozilla.org/show_bug.cgi?id=1717401#c12`](https://bugzilla.mozilla.org/show_bug.cgi?id=1717401#c12:~:text=Calendar%20object%20with%20uid%20already%20exists%20in%20this%20calendar%20collection) \[1\]

1. 

> [@CalDAV API and Trashbin](https://help.nextcloud.com/t/caldav-api-and-trashbin/133755/1):
>
> > Deleted calendar object with uid already exists in this calendar collection.

2. 

> [@Error when accepting a calendar invite on Thunderbird](https://help.nextcloud.com/t/error-when-accepting-a-calendar-invite-on-thunderbird/65117/1):
>
> > `Sabre\DAV\Exception\BadRequest`: Calendar object with uid already exists in this calendar collection.

3. 

> [@NextCloud 14, Calendar - errors in requests to share links](https://help.nextcloud.com/t/nextcloud-14-calendar-errors-in-requests-to-share-links/43872/1):
>
> > `Sabre\DAV\Exception\BadRequest`: Calendar object with uid already exists in this calendar collection.

4. 

> [@Termin Import im Kalender funktioniert nicht](https://help.nextcloud.com/t/termin-import-im-kalender-funktioniert-nicht/137000/1):
>
> > Deleted calendar object with uid already exists in this calendar collection.

If so, this might be mitigated with:

> <https://github.com/nextcloud/calendar/issues/1508#issuecomment-2053638832>
>
> \- Before importing, send request with all UIDs to the server. (or maybe not all …but 50 at a time)
> \- If it doesn't give a 404, parse the calendar-data from the server and compare the LAST-MODIFIED and SEQUENCE-properties of both.
> \- If the version, the user wishes to import, is newer, update the event on the server.
> 
> \<bountysource-plugin\>
> 
> \---
> Want to back this issue? \*\*\[Post a bounty on it!\](https://www.bountysource.com/issues/81351964-import-check-if-uid-already-exists-check-which-one-is-newest-and-update-if-necessary?utm\_campaign=plugin&utm\_content=tracker%2F45525646&utm\_medium=issues&utm\_source=github)\*\* We accept bounties via \[Bountysource\](https://www.bountysource.com/?utm\_campaign=plugin&utm\_content=tracker%2F45525646&utm\_medium=issues&utm\_source=github).
> \</bountysource-plugin\>

However, they stipulate that the current verification mechanism is intra-calendar.

* * *

1. [`bugzilla.mozilla.org/show_bug.cgi?id=1993382#c0`](https://bugzilla.mozilla.org/show_bug.cgi?id=1993382#c0:~:text=Whereas%20the%20bugs.kde.org%20URI%20rendered%20an%20embed%2C%20its%20bugzilla.mozilla.org%20counterpart%20did%20not.)

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