#1 Ranking Achievement Not Registered

When I went to use my gladiators arena tokens I noticed that one of my gladiators were attacked. This attack seems to have moved her up on the rankings to 1st place, but I also noticed I did not recieve the achievement for "Earn(ing) the #1 ranking position in the Veteran bracket." I don't know if I just didn't get the achievement since I didn't "earn" the position or if this is actually a bug. If any more information is needed I will be glad to supply it if I have access to it still.

Yes. Veteran (and others) Champion achievement(s) triggered when Your gladiator stay on the first position after a fight. This make difficult to do this achievement.
But it is not principal. +2 Size have no sense in the game.