Two of same ally, only one gains experience

[TekerSmona]

Playing this on iOS. I have two Allied Bomber Boys (Gunner). Both are four * one is Lvl 80 the other is Lvl 55 (exp only earned through shards). With every single battle using the lvl 55 boy no experience is gained, ever. When at the end of battle review displaying amount of xp gained per character my Lvl 80 boy magically appears and cannot gain experience since it is maxed out. I have tested out different configurations and 20 or so battles and the issue persists.

I would be happy to provide any documentation if it would be helpful.