I get a battle where the two fronts get a bonus for superiority on flotillas number : 

I didn't keep a save previous the battle.

If you need, I will try to reproduce it.

Regards,

Elphealer

Hello :)

I've tried to reproduce that issue, in vain :(

If you manage to repro on you're end that'd be great :D

Cheers and thanks for your help!