Sensor 3 and 4 port DMX Gateway issue

I suspect a broken DMX wire, especially as the rack it telling you that.

Since you are using network somewhere, I might try hooking them all up to net rather than DMX. That's really a separate conversation but it would isolate the racks from each other and assist troubleshooting.

I'd agree about the broken DMX if the 5 other racks that are in the same closet were also spiking output. I put a swisson XMT 120a on the line for a few hours and no errors came up.

The fact that other things work on the line doesn't mean much - only that the cable isn't completely broken.
DMX is very resilient. It will mostly work "ok" in incredibly bad situations - until the show of course, where several fixtures will suddenly go crazy at the worst possible moment!

A broken/damaged core or wrong termination will quite often only manifest problems at particular points on the line where the outoging data smacks into reflected data - which may move along the cable depending on conditions and levels.

Given what you've said, the first thing to check is the actual DMX wiring in all the racks and other devices on that DMX cable.
Make sure all the cores are secure and the right way around (swapping DMX- and common often "works"), that it's a continuous daisychain with no Y-splits and that the DMX termination is correct.

However, as you have a DMX Gateway (and thus a networked system), I would highly recommend not using DMX at all!

It is better to control the Sensor3 racks via the Ethernet network, as then they can report their status back to your Ion and you can even do some basic configuration like setting dimmer curves and dimmed/switched mode from the console.

The fact that other things work on the line doesn't mean much - only that the cable isn't completely broken.
DMX is very resilient. It will mostly work "ok" in incredibly bad situations - until the show of course, where several fixtures will suddenly go crazy at the worst possible moment!

A broken/damaged core or wrong termination will quite often only manifest problems at particular points on the line where the outoging data smacks into reflected data - which may move along the cable depending on conditions and levels.

Given what you've said, the first thing to check is the actual DMX wiring in all the racks and other devices on that DMX cable.
Make sure all the cores are secure and the right way around (swapping DMX- and common often "works"), that it's a continuous daisychain with no Y-splits and that the DMX termination is correct.

However, as you have a DMX Gateway (and thus a networked system), I would highly recommend not using DMX at all!

It is better to control the Sensor3 racks via the Ethernet network, as then they can report their status back to your Ion and you can even do some basic configuration like setting dimmer curves and dimmed/switched mode from the console.

Networking the racks is not an option at this location, the vendor that is used did not supply all sensor 3 dimming. I have quite a mix. I did however extend the DMX for that universe back to the console (removing the gateway from the equation) and the issue seems to have resolved itself. As time permits I will be checking the homerun that feeds that universe to be certain that no further issues present themselves. Thank you for your input.