Hypex nCore stuck in bootloader mode

Hi - I have an nCore based power amp which is stuck in bootloader mode, even when I power cycle the system. This all happened when I was updating the firmware and control firmware. It seems the firmware update completed successfully (v2.3) but the control firmware (v1.4, 1.5b, and 1.6b) produce a CRC error and tries to reload, endlessly. Any thoughts on what steps I might take to break out of bootloader mode? Many thanks