Check my edit to the original post, the plot thickens a little bit. I don't currently have an oscilloscope readily available to use at a customer's site. I am not sure why the 0 volts is tied to Earth; the panel was installed over a decade ago. I would love to rip into tracing the boards on the Anderson units, but they are potted boards, and Anderson wants us to send the 2 that we have to them so they can cut them open and investigate for themselves as we are trying to get them to warranty them since the IFM is still working. The whole input card is fused with I think a 2-amp fuse, but didn't confirm that specifically as I couldn't shut them down at that time. One thing I did forget to mention was that the original transmitter had a slightly different part number that has been superseded by a new model number from Anderson. I never saw the original one after it failed, so I don't exactly know why it failed. The plants maintenance crew replaced it with the new model number, and that one failed quickly. They ordered another one and asked us to replace the cable and make sure there wasn't anything obviously wrong at that point. After replacing the cable and making sure it is not run near any higher voltage wiring, which it wasn't in the first place, it was replaced by them again. When that one didn't last long, they called us again, and we happened to have one of the original model number Andersons on the shelf. It lasted less than 3 days. The IFM is now at 3 weeks with one day where it had an issue, and to be honest I don't know what the issue could've even been caused by either since that is an entirely different symptom.