I have two devices: a Samsung Android tablet and a Moto Android smartphone. The behaviour I describe below does not happen on the tablet, only on the phone.
On the smartphone, the UI is different when I try to level up a costume. My first Sonya (or it is the same for any other hero) is at 7/40 + 19 talents. In the hero roster she is not equipped with a costume. When I open her up for action, she is ‘equipped’ but shows the stats and image of an unequipped Sonya. I can click on an arrow to unequip her, whereupon the image and stats changes to the costume, the button below changes to ‘equip’ (which she is NOT). If I exit then the details in the hero roster show her unequipped and with her full stats.
I can switch to saving her as ‘equipped’ by first hitting an arrow to move her from ‘equipped’ to ‘equip’, then hitting the ‘equip’ button which switches that status from ‘equipped’ but does not change the image or stats. I can exit then and she shows up as unequipped.
This does not happen on the tablet. The middle button - equip or unequip - is not active.