There is some issue with the XO QMK PCB.
Some how it mapping file(.hex) is not working properly and freezes the PCB.
We are try to find out the reason and try to solve it.
But until than please note.
Before flash the file you can check the file is good to be flashed or not.
If you open up a .hex file with note app/program you can see the code like the picture.
If it starts with ":2" it is good to be flashed.
But if the code start ":1" do not flash with that file.
(And please tell me how you make that file and other information)