by using UF2.1 (actually after starting up in the Reader it displays v2.0) creating new image (pressing 5) goes smoothly, problem starts by flashing (6). That's the error msg:
Error while flashing partition! It is recommended to switch to recovery mode and use Sony flasher to flash a stock image.
I found similar problem
here where you suggested that it might be a bad block in the flash.
I might also try to change fonts according to
these instructions. Finally might stay with BD and LRFs.