Darius Grab(E) disables autoattacks

i was playing a ARAM game when i noticed i couldn't autoattack no one, i did some test during the game just to understand what was causing it, i realised i could do all my abilities except my grab, i could grab, but if i grabbed a champion , until i died or disconnected and then returned, my autoattacks were perma-disabled. also my mouse marker remained the same as if i had it on an enemy. i dind't try this on summoner's rift, so i don't know if it happens also in 5 vs 5