Sorry for jumping into your discussion, this is very similar what I had once.
Are you certainly sure you’re uploading correct hex file to Arduino after erasing eeprom;
This one I used and get rid of coordination mistakes. grbl0_9i_X_Carve_500mm_ACME (1).hex (80.3 KB)
500mm doesn’t means anything. After upload successful, I started Easel and setup my machine with correct parameters.
just a thought.