I just got through researching this issue for a client. Apparently it is at least somewhat common, and appears to be caused by RF interference/noise radiating from USB 3.0 ports and cables, which stomps over 2.4 GHz band.

Popular solutions seem to involve applying custom shielding to dongles/cables/adaptors, trying different models of these, or experimenting with their physical proximity and layout. Sigh.

Discussion, including a link to an Intel whitepaper on the topic, here: https://apple.stackexchange.com/questions/329970/usb-c-dongl...