First comment: On or around line 369 in Configuration_adv.h, it looks like you can uncomment "//#define LCD_PROGRESS_BAR" to restore the functionality I think you mentioned.

Second comment: Apologies if I missed something in the preceding discussion..., but it also seems at least possible that you have a genuinely failing bed heater relay. I missed if you mentioned that the firmware was actually reporting a runaway condition..., if it was..., were the HE and bed being successfully de-powered? ..., or did the bed just sit there and cook?

FWIW, I still run the mechanical relay, but I wired it with 10Ga from the start, AND I placed the relay board (and the RUMBA for that matter) on standoffs..., to ensure airflow underneath the board(s) as well. As I recall, MF's instructions just have you screw everything down flush to the wood.