I will ask @Volker at the next München Fairphoners Meetup where we both attend in person (next Meetup I will be on holidays, but the meeting afterwards).
Dismount camera module and clean its contacts with 96% vol alcohol.
Full story:
This happened to my FP3 (non +) while I was having trouble to charge it months ago.
The problem seemed to go away after dismantling and cleaning all contacts with alcohol, which is how I solved the charging issue.
There was a software update around the same time so I cannot be 100% sure.
I observed the issue a few days ago but it is not happening right now.
I am using the latest update since today.
Today I received the monthly security update for my FF3+
After the update the Flashlight works normally!
In the past I have re-booted my FF3+ several times, but only the software update solved the problem.