Ranger pvp Bug
I’ve seen this bug a few times too – try resetting your traits in The Mists and then reallocate them all. So long as you have your build set before you enter the first match after resetting this doesn’t seem to happen.
I think it’s not a bug. What happens is that when you use the same traits for pvp and pve, they overlap so they go blank to re-set. Since the characters dont seem to have an internal memory for two types of traits, they just go blank to avoid problems.