Impact Shot Bug

I don't know if it has been discussed before but it seems the Impact Shot either has an incorrect description or is bugged. It seems to root the target in place before the pushback, I'm no talking about the stun on the 1st shot from stealth, but the regular out of stealth IS, the target gets rooted for abour 1-1.5sec before the knockback after the knockback it is possible to IS again and apply the same root and chain shoot the target 4 times preventing it from moving for like 3-4 seconds, and I REPEAT THE ROOT OCCURS BEFORE THE KNOCKBACK AND WHILE NOT SHOOTING FROM STEALTH! It should not be like this the knockback is fine but the root is very bugged and there is nothing about this in the description.