Hello Michael and Julian, that explains why the behaviour of "RandomizedDelaySec" together with "Persistent" is different between buster and bullseye. If that's the intended behaviour, my systems seems to work like they should and it's no bug. So for me I will change the delay from 12h to maybe 5min. I think that will fit better to my use case. Thanks a lot for your research and explanation of the timers.
Regards Hendrik
