I can’t say for sure what your issue is, but a PC is known noise source, a USB cable sends digital information form the source to the target, but it also sends power, and the PC can pass along nose over the power line. I’ve been using my PC attached via USB for many years, using a Sonore microRendu USB Isolator, which filters out the nose. Here’s a link to just one of the many USB isolators you could try out: https://jcat.eu/featured/usb-isolator/
I also noticed there is a microRendu General Thread: microRendu General Thread
Also if possible, I just recently switched away from USB, not that there is anything wrong, but I’m now using the Ethernet cable to communicate to my Roon Ready Dac, thus if your target Dac is Roon Ready, you may have an even better option available.