The title describes the essence.
If you get stunned while using Lunge, the running animation disappears if the move button (LMB) has been held down all this time. If you stop and start moving again, everything becomes normal.
That is, the problem is in the logic, after moving with the help of Lunge, the character should have played the skill completion animation, but having received a stun, he interrupted it with a stun animation.
I will not attach bug reports and videos, since the bug is easy to repeat