[Bug]: HTTP REPORT returns 503 on some CalDAV/CardDAV collections

[rfc2822]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I create this ticket to track the "Nextcloud returns 503 on REPORT for some collections", see bitfireAT/davx5-ose#285, as discussed in Talk today

CC @ChristophWurst @miaulalala @st3iny

Steps to reproduce

Unfortunately not known how

Expected behavior

REPORT should return 207 or at least some error message

Installation method

None

Operating system

Other

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

not available

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

[nickvergessen]

Also my thunderbird is now not showing all the events any more that exist in the web. The report request does show a 207 in this case, but something is still going wrong:

2001:…:7c70 - - [20/Mar/2023:07:41:45 +0000] "REPORT /remote.php/dav/calendars/joas/personal/ HTTP/1.1" 207 1198 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0" 259643

[manswiss]

My synchronisation on Android with DavX5 has also stopped working since the update. I also see the 207 and 503 errors in the log.

[Der-K-2000]

I can confirm this issue since RC 2 (I switched from v25 stable to v26 RC 2), with all mobile apps connected to DAVx5 (Android/F-Droid) and with Thunderbird, too.

Also there are no changes after checking and resetting everything or refreshing the password.