yeah mine does that, where it kind of quivers with excitement, w/the head off the ground a bit and all, as if its caught in a dilema of striking or waiting for a better moment/position to, right before it actually does. I think its normal, it's never been a concern for me.
Also, I too have had a f/t explode on me, I just tossed it and got a new one, as I thought that would be the easier route than going and having to clean most the cage after.