ATEM Mini Corrupt webcam input

My ATEM Mini produces signals properly to HDMI output, but scrambled video on the webcam output to my computer. This seems to be independent of the input used - I am using Nikon and Olympus DSLR sources over HDMI, sources work fine to other destinations including direct to computer via Elgato input card, but not through ATEM.

Any help appreciated.

24 hours on, with a bit more sleep and a little luck....turns out my computer has a bad USB port. Rather annoying, and yet easily remedied.