Have you tried replacing the EZ-45s like you mentioned you were going to?

I've seen problems with these connectors before when used with certain products. Sometimes the cut-off ends of the eight wires stick out ever so slightly and cause a short of some sort at the base of whatever they're being plugged into.

Other times, not all 8 pins get fully crimped on the EZ-45 probably due to not crimping hard enough or from a bad or worn-out die.

I know these connectors are super easy to use but I stopped using them a long time ago. It's not that hard to terminate a standard RJ-45.