3ds Max Animation Jitter

Hey guys,

I have serial shots I animated using the same model and in almost all of them the head and tongue of the model jitter/twitch around like crazy. The problem is that its pretty random when this occurs even if I go back to look at the frame it happens on the issue isn't necessarily there and may occur on different frames. Any idea what could be causing this?

I'm using 3ds Max 2013.

Thanks guys