VFREEBUSY reports me as busy even though I have no events on the day in any calendar.

Steps to reproduce

<?xml version="1.0" encoding="utf-8"?>
<cal:schedule-response xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns" xmlns:cal="urn:ietf:params:xml:ns:caldav" xmlns:cs="http://calendarserver.org/ns/" xmlns:oc="http://owncloud.org/ns" xmlns:nc="http://nextcloud.org/ns">
  <cal:response>
    <cal:recipient>
      <d:href>mailto:miau_lalala@gmx.net</d:href>
    </cal:recipient>
    <cal:request-status>2.0;Success</cal:request-status>
    <cal:calendar-data>BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Sabre//Sabre VObject 4.4.2//EN
CALSCALE:GREGORIAN
METHOD:REPLY
BEGIN:VFREEBUSY
DTSTART:20230120T230000Z
DTEND:20230121T230000Z
DTSTAMP:20230116T122046Z
FREEBUSY:20230120T230000Z/20230121T230000Z
ATTENDEE:mailto:miau_lalala@gmx.net
UID:d06786fa-6daf-4798-bbfa-412d79c3382e
ORGANIZER;CN=admin:mailto:miau_lalala@gmx.net
END:VFREEBUSY
END:VCALENDAR
</cal:calendar-data>
  </cal:response>
  <cal:response>
    <cal:recipient>
      <d:href>mailto:test@trash-mail.com</d:href>
    </cal:recipient>
    <cal:request-status>3.7;Could not find principal</cal:request-status>
  </cal:response>
</cal:schedule-response>

Not sure yet, but I'm assuming having an all day event or a recurrence previously and deleting that is what causes this issue. I will debug it again further.

Or this might simply be a UI issue?

I think this might be the cause of the appointment bug we have seen before where a user can't book an appointment if the calendar of the appointment owner had a event that was deleted previously.

@ChristophWurst does the VFREEBUSY component have it's own UID or is that the blocking event UID?

Expected behavior

I am free in the VFREEBUSY overview.

Actual behaviour

I am busy in the VFREEBUSY overview:

Calendar app version

4.2.1

CalDAV-clients used

Web

Browser

No response

Client operating system

No response

Server operating system

No response

Web server

None

Database engine version

None

PHP engine version

None

Nextcloud version

No response

Updated from an older installed version or fresh install

None

List of activated apps

No response

Nextcloud configuration

No response

Web server error log

No response

Log file

No response

Browser log

No response

Additional info

No response

Reproduce the issue using the supplied VFREEBUSY schedule-response and compare the result with the expected free status. Trace the free/busy calculation from that response; done means a deleted or previously recurring event no longer marks an otherwise empty day as busy.