Update from my previous post:
Testing with an 18i20 was inconclusive, as I was unable to even get the 18i20 running.
HOWEVER, and I hesitate to even post this, lest I jinx myself, but I believe I’ve located the issue and it is with Intel’s networking drivers for their integrated LAN hardware. Uninstalling the device from Device Manager fixed this for me (fingers crossed that I didn’t just jinx myself).
Hope this helps!