When you will be hitted while you are shooting with your xbow it will be jammed
I heard shooted bolt sound (but no bolt were shot)
shows that you don't have ready bolt on your xbow (red dot) and when you are trying to put a new one it shows shooting animation
so, you can't shoot (no bolt on xbow) and can't reload it
it happens to me many times
sometimes throwing out an xbow and take it back helps, but it's very rare