WC4 GOG - Cut scenes no longer visible when streaming with OBS



I've been streaming my play through of WC4 (GOG version) on Twitch using OBS. Last week in the middle of streaming the game OBS flipped out. When I got it back up and running, everything seemed to be working fine until a video cut scene plays. I can see the video playing on screen but OBS will just show a black/blank screen (audio is unaffected). Once the cut scene ends, the picture comes back up like nothing has happened.

I've tried playing around with the capture window properties on OBS as well as looking at the compatibility options on WC4 but I just can't work out what the issue is. Has anyone got any clues what could be the issue?