My FP3+ gets sometimes hot during the last days, though the room temperature is below 23°C. The hot area is in the lower part. LineageOS(+microG) gives me a short on screen warning that the power is reduced because the phone is too hot. I always have enegy saving activated so the battery lasts longer.
One time when the phone got hot I was in a building where the mobile data (4G) was available but quite weak. Sometimes even an audio stream broke because the connection was lost. I guess the modem was transmitting with full power.
Did persons with a sudden death experience similar problems?