Oh!! the bug is maybe caused of this :

PvP was melted with pve : in pve you can join maps 30-35 when you're 28 and you can gain xp until 37 :O
Imagine a LvL28 made a pvp map, and that pvp is "melted" to pve like above, it means a lvl35 would be able to join a lvl28 map, as a lvl23 would be able to :O

Follow me? xD (if you didn't understand, Don't worry... I don't even know if I understood myself lol )