Here is the link to the three files I've had trouble with the most (actually, I have not completed one successful print). I'm leaning more towards a bad contact with the thumb drive. In darker rooms, there are two lights on the stock motherboard that are pretty easy to see. One I believe corresponds to interactions with the USB drive, and I can turn it off or dim it just by slightly jiggling the USB drive. I guess now the next step is to go over the connections.
I have another thumb drive that is much smaller and fits more securely, but I'm having problems with it as well. The CubeX can see the files on the drive, but it won't even get to the file checking step before it gives me an error. Is there a special way to format it? I have it formatted as a FAT currently.