Frustrating OBS Recording Issue (audio but no video)

I've been using obs for a while now, but something that keeps happening (seemingly randomly) to me where it will record all my audio channels fine, but there is no video. There is just a single frame used as a thumbnail.

Has anyone run into an issue like this, or does anyone know how to stop it from happening? Any help would be greatly appreciated!

Context: Recently, I got some old friends together to explore our old Minecraft realm, but not everyone could make it, so I wanted to record it for those who couldn't be there. Now I'm really disappointed because it didn't save any video and only captured one "frame" right at the beginning.

When this problem happens, the one frame it saves is always on pause/menu screens, or right when I "Alt + Tab" to different windows. I've had this happen in other places, not just Minecraft. I've never had a "partial" recording; it either happens or it doesn't.

PC specs and Recording environment:

Windows 10, 1650, 9th gen i3.

I am recording to a HHD in the .mkv format and I remux the video to .mp4 with 4 separate audio channels. Filmora (my video editor) supports both .mp4 and .mkv formats.

-Thanks