Guild Wars 2

Is there a DR after the use of a Stun or Knockdown?

I ask, because I noticed when playing my warrior in SPvP, that sometimes in situations where I bull charge the target and knock them down,
And the. Shield bash right afterwards, the shield bash’s stun doesn’t register.

And vice verse when leading with Shield Bash then Bull Rush.

What’s going on? Is there a DR in play that I don’t know about?

http://wiki.guildwars2.com/wiki/Stun

Despite its in-game description, there is no evidence that the duration of stun stacks.

I’ve found this too, it doesn’t seem as though stuns actually stack duration, needing to be reapplied when the previous one is about to expire.

As an aside, I find this to be better from a game design perspective, as it requires more active play from the stun-locking player.