Filiberto C, Marc P, Robert S
We tracked the failure to an XLR cable that runs between the LEMI breakout black box and the FIBOX. Upon inspection we found that the connector had two broken internal wires. We repaired and reinstalled the cable and everything looks goodish. There is still a 300Hz - 500Hz lump on the X channel which we hope will go away once the LEMI has a few days to warm up. Attached is an image of the broken connector.
We verified that the lump originates upstream from the FIBOX.