Do an offline firmware upgrade, follow these steps:
- Put Midihub in bootloader mode by turning it on while holding down the button. All LEDs will be on in this mode.
- Connect using 1.15.3 Editor.
- Do Device → Flash Firmware…
- Give it the .bfw Firmware file from the 1.15.3 release.
- Once done, reconnect to Midihub, it should already be running 1.15.0 Firmware with blank memory.
- Do Device → Import Everything… and give it the fixed up .mhd file I sent you via PM.
Afterwards it should work well again.