[Bug]: Calendar events not showing up for invitee

⚠️ 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 OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Hi,

On NC 29.0.0 beta 3, Calendar events are a bit unreliable. I create an event and add another user as an invitee. The event doesn't show on his calendar. At the same time, lots of this shows up in the log when creating the event:

{"reqId":"R7laQWgrMPrjeqLisVWl","level":1,"time":"2024-03-16T15:44:14+00:00","remoteAddr":"10.100.21.115","user":"admin","app":"no app in context","method":"GET","url":"/ocs/v2.php/apps/notifications/api/v2/notifications","message":"Notification was not parsed by any notifier [app: ransomware_protection, subject: help_requested]","userAgent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:123.0) Gecko/20100101 Firefox/123.0","version":"29.0.0.9","data":[]}

I have uninstalled the ransomware_protection app, and still have the same behavior.

Steps to reproduce

1. Create calendar event and add another user as invited
2. The event doesn't show up, the user doesn't get invitation

Expected behavior

The user should get a notification by mail and the event should show up in his calendar.

Installation method

Community Docker image

Nextcloud Server version

master

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.1

Web server

Nginx

Database engine version

MySQL

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

Upgraded to a MAJOR version (ex. 22 to 23)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

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

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

No source file, test, or entry point is identified in the report. Start by reproducing the missing invitee event and notification on the stated Nextcloud, PHP, MySQL, and LDAP/SSO setup, then trace the calendar invitation and notification logs. Done means the invitee receives the mail and sees the event in the calendar.