One thing that I noticed on a Taz Pro that I was giving a once over after the calibrators got done with it, was that the ground screw that connected the USB thumbdrive to the RAMBo was not tightened all the way. I'm not sure if this could cause the thumbdrives to short out, but it's a thought.
When the ring terminals of the added ground wires are attached to the screw points of the RAMBo, LCD and USB boards, care needs to be taken that the metal parts of the ring terminals are situated in a way that they do not contact any of the components on the board. This can happen when the terminals are turned toward components. On all the boards, there are ways to attach the terminals so they avoid components.
@mjpelletier can you review the OHAI and see if there is a way to be more clear in how we explain how this is built to help prevent this? https://ohai.lulzbot.com/project/control-box-assembly/quiver/
@DaniAO we got that printer back to R&D. Out of the box the USB reader was not working. However, we didn't see any issue with the USB drive after; it worked fine on a computer.
@mjpelletier then replaced the USB ribbon cable and powered up the printer and the USB reader worked fine with the new cable. Where it gets bizarre is that Mark tested the original cable and then put the original cable back in and the USB reader continued to work. We think that original ribbon cable was not clamped completely in the connector and removing the cable shifted it around to make the connection work.
To be clear, the previously mentioned ground terminal is not the issue with this printer.
Mark is continuing to review the printer but we think completing T5883 is the answer here. As far as I know, we are not currently testing these ribbon cables.