I have the same problem on FP3 (Signal messenger created local backup file overnight, which clogged memory to 100%). Upon starting the phone, there is a 3-second window to use it, then the system shuts down. Going into safe mode doesn’t help.
My bootloader is locked and the device encrypted, and therefore cannot access any meaningful files within ADB. TWRP image cannot be used. I followed this thread without much success: How to mount encrypted /data partition in recovery mode? - #82 by tcecyk
Does anyone have further ideas other than wiping the device?
This was on e OS T, latest. Is there any chance that this memory clogging issue could be fixed in a future release?