CalDAV Export to *.ics file not working with empty PidLidAppointmentTimeZoneDefinitionEndDisplay value

[ledlinge]

I am trying to export my grommunio calendar to an *.ics file unsing following URL:
https://my.server.name/dav/calendars/@/Kalender?export

However I just receive an empty (0 Byte) *.ics file and lots of errors in /var/log/syslog:

2025-11-20T23:20:05.308453+01:00 grommunio gromox-zcore[52516]: E-2202: oxcical_export /var/lib/gromox/user//:m8577981801094447105 failed
2025-11-20T23:20:05.349599+01:00 grommunio gromox-zcore[52516]: E-2209: PidLidAppointmentTimeZoneDefinitionEndDisplay contents not recognized

After digging into my calendar-entries using mfcmapi software I found that PidLidAppointmentTimeZoneDefinitionEndDisplay is NULL (empty).
I guess gromox-zcore cannot handle this and is expecting valid timezone-data within this value.

However all those entries has been created either using Android mail app or Microsoft Outlook.

Please investigate whether it's possible to handle the case of empty PidLidAppointmentTimeZoneDefinitionEndDisplay value when exporting *.ics files.
Probably the same holds true for PidLidAppointmentTimeZoneDefinitionStartDisplay value.