Guild Wars 2

I’ve had the knockdown-problem against other bosses apart from Kieldia, and from what I’ve noticed, it is entirely dependent on what area your arena is over. Some of the legendary bosses knockdowns seem to propogate to the arena (this is just my speculations, but it seems reasonable.)

Just doing the Gauntlet from the arena over the centaur area has stopped all of the knockdown-issues I had in any other arena.

This may not be the cause of your problems, which could be some bug related to Kieldia, but you could try changing to a different arena and see if it helps.

I was a bit puzzled by this as well, but according to the Wiki you are rewarded for 100 points as well as 500, so my guess is the 1000 chest is going to unlock tomorrow.

http://wiki.guildwars2.com/wiki/Achievement_Chest