I don’t do video capture, but checking around there seems to be at least two workarounds to test:
1. Use an external usb 3.0 hub. Seems certain usb3.0 chipsets are not compatible with certain cards.
2. Use the hdmi input of any generic scart-to-hdmi scaler. This will normalize the signal at the cost of some colour accuracy and frame conversion. Obviously use an hdmi splitter before the generic scaler so you dont have to play with the extra lag. I.e. OSSC -> splitter -> generic scaler -> capture card.
See the capture card compatibility thread for more info.