This is a response I got from another forum:
I don't know what those errors mean, but in Q3A you need to do
g_synchronousclients 1; record; g_synchronousclients 0
You can leave out setting it to 0 but it's better for movement.
I know your errors don't refer to these settings specifically, but they may be the equivalent in JK2, so you could try them. Alternatively find the equivalent commands for JK2, if they are different.
You say that after it restarts it works, though, so I don't know, it could be a graphics driver problem, cause restarting can be a video restart (vid_restart).
The !CL,Snap.valid, I have 2 guesses for. It could be a screenshots problem, where "snap" refers to a screenshot. Maybe he has screenshotjpeg switched on - so it saves screenshots as jpegs instead of tgas - and that is the problem. My other guess is it could be something to do with his /snaps setting, which is to do with network conenctions. Try the default snaps setting (type /snaps and press Enter and it will tell you the default aswell as the current value, same as with any command).
judging from griff's and this reply, you might wanna take a look at the recording script you're using (assuming you are using one), to make sure it's imputting the correct commands.