Gave it a try, unfortunately no change (exactly the same error logs).
We ran “univention-app register horde=5.2.7-3” (since the problem sounds related to finding applications and solved an update problem here Docker - Horde - Login_problem), might that cause troubles now?
We’ve also upgraded to 4.3-2 errata234.
Please advice (the system runs for a customer we initially convinced to switch to an UCS installation instead of Windows… now too many calendar related problems (in particular when moving appointments) already disappoints them and we hope for stability improvements in this regard with the horde upgrade).
Thank you.