I re-read your original question some more, and I think it might be capturable on video. If you can do that, and catch both when you say it works and when you say it doesn't, it should clear things up.
You might not be able to record with OBS, if that's the "failure trigger", but a "potato cam" of a phone watching the screen should be enough if you have to resort to that. Frame it "well enough", and keep it still, so the phone's terrible motion handling isn't (much of) a problem.
Better, if you already have the gear to do it, would be to run the misbehaving computer into a video capture device on a different computer, also running OBS to record *that*. And depending on your workflow, that might even be an "okay" workaround.