As said - in the long software identifier there is number 43 - that is the newest software - bad.
The other camera has 29 which works OK.
The software I got from support is 30 and seems to be ok since 3 days.
So yes - installing older software fixed the issue. That's why I provided the warning.
I have spent some time investigating the problem, so now I share the results.
The first step that caused the disaster was clicking "Update software".
The newest software V2.800.0000000.43.R, Build Date: 2023-08-29 (DH_IPC-HX3XXX-Leo_MultiLang_PN_Stream3_V2.800.0000000.43.R.230829) was installed...