FP3+ switches off regularly

After upgrating wirh the latest OTA, FP3+ regularly switches off, mainly after disconnecting from chargers.
Needs to remove battery to start the phone again.

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

I don’t have an immediate idea about the issue, but keeping the power button pressed for about 15 seconds should force a reboot in any situation.

Is there any way to prevent this undesired switch off, please?