I don’t know for sure, but an inexpensive, unmanaged, ethernet switch might help isolate (router to switch, switch to VEGA.
Fiber would isolate the router electrically from the VEGA. I use a pair of TP-Link Media Converters:
The MC200CM, but the MC100CM would work just as well (there are also some other, cheaper brands). Connect them with a length of fiber and the whole package is around $125. Since the electrical signal is converted to light pulse then back to electrical, any noise from the router would not travel to the VEGA and, I assume, it would break any ground loops that travel on the ethernet cable.
You might troubleshoot and find a way to eliminate the noise without cost, but the change to fiber lowered the overall noise floor for me and is a worthy tweak regardless.