Safe Mode just disables all third party installed apps, so can exclude an app causing the issue.
faulty SIM or SD cards can cause unexplanable multiple issues (FP has a guide for this at least for FP3 on its support pages and suggests a SIM card older than 2 years gives a higher likelihood to cause issues).
I haven’t, looks like this would be worth trying, but I’m back to resignation. I guess this is for nerdier folks than me. I’ll sell it for cheap. Thanks anyway for you great support!