It seems like the program becomes corrupted after you flash the Coldcard Q and then it works just fine then suddenly the screen stuck on the black screen it looks like the bootloader issue it can't start because of the corrupted program.

The documentation from Cold Card seems does not have any way to hard reset this wallet and according to them there's no way to reset the pin meaning we can't reprogram this hardware wallet after a deep research I found a guide where you need to burn the recovery image for this unit I think this will help to revive this unit.

Check this guide from their github here https://github.com/Coldcard/recovery-images
Take note of recovery images you can download them from this link https://coldcard.com/downloads/recovery