Not sure if this has been posted here before, did a search didn't see anything on the first few pages. I've reported this with /bug three times in the last month or two, but it still hasn't been fixed as of today.
On the FSC levels (I'm not sure if it happens on other levels by other monsters, I primarily do FSC runs), when a Trojan or Vanaduke hits me with their weapons I often get stuck for about 3 seconds before the stun effect comes into effect. Let me make this clear....I get hit, then I cannot move, face another direction, use any vials, pills, nor remedies for about 3 seconds....then the stun effect happens, I can move with the stun animation and the reduced speed caused by the stun. I know that the stun effect is not supposed to make you get stuck for 3 seconds before the stun effect starts, it was not like this before. I can only assume this is a bug that needs to be addressed, because if it's an intended effect of stun from now on....it is totally unfair as I can't even use a remedy to remove it and usually I get wacked repeatedly while I can't do anything and I'm dead before the real stun effect starts.
Simply a strong stun having effects. It's normal to get completely stuck for a few seconds when stunned in Tier 3, it's note as Stun Lock. Not a glitch, it's intented. (And you won't believe how fun it is to do that in Lockdown with a Callahan charge :P)