This has happened a total of 3 times. I noticed the third time because I was trying to show my friend (who was in the room with me) the gestures using the F keys. To illustrate this I double tapped ALT so I could pan around. I noticed that the F keys above F4 weren't working and upon my character not performing the gestures, he proceeded to lock up.

The friend I mentioned said not to do that because that's what I did the last time it locked up, which lead me to believe it was a consistent bug. But I just tried to reproduce now with no success.

Only thing that is consistent is that there's a few seconds delay between hitting F keys and then seeing their corresponding gesture.

Additional: the first time my character locked up was when I'd pressed the 'G' key - he threw the axe he was holding, then spontaneously fell down and the same thing happened - he locked up. Panning around is possible in this state but no movement whatsoever.