The Longest Day achievement problem

[Colar]

I am having trouble with the Longest Day achievement, where I have to fight so many trainers in a day. Some trainers won't fight with my main (a horde). I was able to get the battle with an allied toon but the achievement only reflected single toon, not account wide. That is, what I defeat on my ally doesn't show up on my horde main, and what I did on horde doesn't show up on ally.

I used to be able to fight them all before I transferred server.

Is there a way to make the trainer behave better? Or is there a bug somewhere?

[Colar]

Derp I need glasses. The list for horde and allied players are different. The NPC I couldn't fight are for allies only.

[Fubar]

I actually did this over a few days, for some reason it bugged and kept the battles I'd won the next day... I didn't get the stone so I ticketed the GM who sent it me (and I didn't mention the bug). Mwah ha ha ha!

[Casca]

Not sure it's a bug, I read somewhere it's meant to be done within 24 hours of play time not real time.