Movement keys (WASD) appear to get stuck in the logical down position.
So you end up stuck in a moving state and you have to press the 'stuck' key to stop moving in that direction.
My friend and I have both experienced this recently in DayZ which leads me to think it's a DayZ bug, introduced quite recently.
It's only happened to me a couple times but it's particularly prevalent for my friend.
I'm not sure if it's possibly worsened for someone who drops more frames?
I know this can be an issue if the main game loop momentarily stalls, it may fail to see the key up event.