Since you have a PROG button on your PCB, that indicates to me you have a v2.3 or v2.4 CM controller. While I never tried reflashing my v2.3 CM controller, I had fits getting a v2,2 controller reflashed for alternative CNC controls. I came to the conclusion that the bootloader was corrupt and/or inoperable. Luckily I had an AVR JTAG-ICE unit so I could reflash the bootloader. I documented this process here:
This may be your fault and thought I’d give you something to consider for remediating your issue.