I did change to EVERY damn port on the M/B.
Turns out it was the USB hub power brick. It's powered by a USB-C so i was using a phone charger that happened to be JUST sufficient. It was flimsy enough that it would eventually give up and stop sending 5V reliably, causing the whole issue. A different power source seems to have solved all issues.
To restate: the Rhino was definitely NOT the cause.
Thanks for taking the time to interact, @walmis. 10/10 would buy a second Rhino. (it's a joke...)