The device that I fixed hasn't had any problems. It was only a day and a half of testing, so there is still a chance that it'll fail. We'll see. But I figured I'd post a guide of what I did because I'm definitely going to try this with the others that stop scanning.
So, the device I was using would rattle occasionally. It would work for a while, then it would stop scanning. A restart wouldn't fix it, but it would scan again if I took the scanner battery out and put it back in. However, that was just a temporary fix and it would stop working after a while. We noticed a that the bad myDevices would rattle, so I took it apart and took out the loose piece. Here's how.
Use a torx driver (size T6). Our store was able to order one that we keep in TSC. You'll need to take off three pairs of screws - all with a T6. Two on the front at the top, two on the back at the bottom, and two more on the inside. After taking out the four screws on the outside, you can pop open the myDevice with a little effort. The last two screws are on the top of the board. The board itself will not completely come off, but you just need to slide the bottom of it to the side a bit. You'll be able to see that little metal cover somewhere inside. Take it out. It doesn't seem to be able to go back on, and I know I'd get glue everywhere if I tried to glue it. Plus, the piece doesn't seem to be important.
So, here are some thoughts. My guess is that while the piece is not important, it could screw things up when it's loose. It might be messing with the electricity somewhere and that's what's causing the scanner to stop working. Also, I have a feeling that the developers would be unlikely to encounter this problem. The piece probably broke off after we dropped it a bunch of times (plus it still works occasionally, so dropping it wouldn't seem to be the cause). Can someone tag the devs who read this site? I don't know who all of them are anymore. I'd like to hear what they think.