Right now it's still a question if this bug even happens. So my focus on that. If it's really happening then I would worry about narrowing the details down from there. There are people saying they see it multiple times a day, if I were them, I'd be motivated to prove it just to get it fixed.

If I saw the Grokko thing in real-time (victim flees after one round of trip with no explanation for it), that would certainly do it for me, guess you have to decide how much you think is necessary here.

For recording I'd use shadowplay, download geforce experince to get it if you have an nvidia graphics card (or use ReLive on AMD), you can set it to constantly record the last few minutes of the screen (it won't capture only a mud-client window) and press a hotkey to save it.

It is pretty simple to use and setup. If someone is concerned about their privacy, they can either crop the video afterward, which is not as much work as it sounds like, or actively record the mud-client window with OBS instead.

As for uploading it, I mentioned streamable because it doesn't require an account, is trustworthy and will compress the filesize without butchering the quality. Youtube, marked private and only email it to an imm who agrees to receive them for the paranoid.

The carnac thing is a good idea but it's too much to ask, and it should be obvious from how the game responds if they're doing anything extra.

So my instructions would be simple:
When the bug happens (grokko tier, guy fleeing 1 round after trip), right afterward show your gags and triggers, then save the recording, include the last 2 minutes before the part where you think you see the bug. Upload it, send link to imm, include in the e-mail body the timestamp where the fighting starts.