Flip lines one and two and see if the problem follows the line. Been a long time since I worked on OnyxVS. If memory serves they use modular connectors which can be prone to have issues. Could be a bad port or a bad crimp on a modular connector. Comcast is notorious for using stranded connectors on solid core wire that can cause issues. If it's the CO module I'm sure refurbs are all over the place. VERY common systems back in the day and were like tanks.