It happened with these NPCs so far: https://classic.wowhead.com/npc=9166/pterrordax#abilities ; https://classic.wowhead.com/npc=9167/frenzied-pterrordax#abilities
When the flee debuff (on me) wears off, my character keeps running and most of the time i don't have control over my movement (pressing w a s d doesn't do anything, i keep running). Then after like 1-3 seconds i regain control over my movement.
Edit: I have to mention that sometimes this doesn't happen...It's randomly occuring. Today it happened almost all the time when i fought them.