Plugins stop working after restart (not always)

[slowtraveler]

Version:2023.2
Platform: Fedora 39
Plugins: NUT_UPS and several SVT based plugins
Description:
Setup is working for several years flawlessly. From about 3 weeks i noticed that sometimes all plugins are stop working...
Log is free of errors..
Receiving data from external sensors (from internet) is OK even when plugins are not working.
Restart of domoticz when plugins are not working takes very long time (more than 2 minutes)...
And often restart solves the problem.
If i restart domoticz when everything is working well i had a two cases:
1. Restart almost immediately - Plugins will not work. In log i can see Worker thread started, but not listed any following actions of plugins
2. Restart takes normal 2-3 seconds for restart - Plugins will work, and after Worker thread started i can see real data obtaining and so on..

When plugins are not working, restart takes long time and it can solve the issue. I can't catch the case where it works... Sometimes - several restarts are not solving the problem. In the other cases - i can make several restarts withou issue to re-appear..

I use cron job for daily backup of database, which stop, backup DB and start the service. So often after such procedure plugins stop working...
Maybe it's some Python issue? Can someone give me a hint where 'to dig'...
Where can be located the problem and how to debug further the reason of this issue?