Presence status updates do not work or show incorrect status

Steps to reproduce

1. Create an appointment
2. Add attendee to meeting
3. Click accept button in mail

Expected behavior

1. The creator of the appointment receives a confirmation message "accepted"
2. The resence status in the calendar view of the appointment updates to "Invitation accepted" (DE: "Einladung angenommen")

Actual behavior

1. The creator of the appointment receives a confirmation message "accepted"
2. The resence status in the calendar view of the appointment is still "Wait for answer" (DE: "Warte auf Antwort")

Sometimes after some time, I don't know when and why, the already accepted appointment of a invited attandee shows the status "Invitation declined" ("DE: Einladung abgelehnt")

In short, the status display is unfortunately completely unusable as it is simply not correct.

Calendar app version

5.1.3

CalDAV-clients used

No response

Browser

Firefox 136.0

Client operating system

Linux Mint 22.1

Server operating system

FreeBSD 13.4

Web server

Apache

Database engine version

MariaDB

PHP engine version

Other

Nextcloud version

30.0.6

Updated from an older installed version or fresh install

Updated from an older version

List of activated apps

Nextcloud configuration

Web server error log

Log file

Browser log

Additional info

• PHP engine version: 8.3
• No error/warning shows up and no suspicious log entries
  • Not to be confused with #3774 and #6568

Start by reproducing the appointment acceptance flow and checking the calendar view for the attendee's presence status. The issue names no files or tests, so trace the acceptance and status-display entry points while comparing the expected accepted state with the stale or declined states. Done means accepted invitations consistently show "Invitation accepted" and do not later change to an incorrect status.