Stability does not work...
I’ve seen similar things happen in Ascalonian Catacombs; specifically with the Graveling Scavengers and their knockdown bite. I’ll pop “Stand Your Ground” and still get knocked-down. http://wiki.guildwars2.com/wiki/%22Stand_Your_Ground!%22
This could also be a timing issue; difference between when the server thinks I activated it and when the Scavenger hits me with its ability.
Xyssi – Asura Guardian
Xystus Furtim – Human Theif
Server: Stormbluff Ilse
Xystus Furtim – Human Theif
Server: Stormbluff Ilse