While I don't do it myself I personally don't think it's a big deal. Either they were left over from a siege and your faction didn't check the keep afterwards or they used ambush or chains which Zos has known about for years and either can't or won't fix. It could have been done accidentally or on purpose, either way kill them and move on.
Kuramas9tails wrote: »Haha. Just a Nightblades gap closer through lag. Believe me, when we get through the door on accident, we freak out once inside because if there's a zerg over yonder, we gone. But if there's no one, we happy.
For the record this guy was out side door, I went in and 5 seconds after (I cast a couple heals on my self) he came through the door. He did this twice.