Help my capture card glitches when capturing n64

[Mc_jackham]

I am trying to capture video from my N64 to my laptop using a cheep amazon AV2HDMI Up scaler into a EVGA XR1 Lite capture card. When I got into streamlabs and looked at the footage it was constantly flickering between good looking video and super dark terrible looking video. I've tried the capture card on its own and it works fine so that's not the issue but when I tried just the upscaler the problem stayed but when I switch to a newer console like my original Xbox the problem goes away completely. Is there anyway I can fix this issue or do I just need to buy a new upscaler? Included a video showing the issue with the N64 and it working normally with the Xbox.