Hi !
It also happens very often with the Jedi Knight Guardian. For instance "blade storm", "force leap", just to quote these two also have a problem.
The Jedi starts his/her move, then reset and eventually strikes down his/her opponent.
I opened two threads to discuss this matter which seems to be really serious.
I even sent an in-game ticket to Bioware in hope to see the bug fixed, even if I am more and more hopeless to see that matter resolved