Where: In the lowest floor of Raduta Keep ramparts. Behind the 'high' DC door. Specifically the leftmost chest.
When: When using the chest as it's unlocked. It might've been because the server has been up for a bit, but I don't know if that's true.
What: The trap, for some reason, isn't counting Evasion as a feat. The damage is still taken even though the check is passed.
Recreate: Try going there with a character that has Evasion, testing it against the other containers.