FP4 slowly dying - which replacement pieces

Hello, just a few random thoughts. Your phone still has a warranty but I imagine it might be difficult to process that on a short visit. But how about meeting with some local FP Angel(s) so that they can have a look?

I would get a spare battery anyway since shipping at a later time might be an issue. Have you used any app like AccuBattery to check the parameters?

Is the reception differeny in California? and how old is your SIM card?