I’ve been using the flash drive that came with the Snapmaker. I have several gcode files on it. It doesn’t always display all of the files on the drive. Scroll forward and back in the file directory. Eventually, the flash drive file listing code got into a state where it wouldn’t advance to the next page of the file list, nor return to the previous page. I had to power cycle the printer to get it working again.
I have firmware version 2.11