Not sure how to screenshot it from a phone, but the Max Level button for my fully covered 3* characters usually shows Level 166. I’ve just levelled up a few from 128 or 129 to 130.
I suddenly noticed the the max level button changed to show a max level of 165. I did an extra level on a character and looked back at the button which then showed a max of 164. Did it again and now the max level button for fully covered 3*s shows 163.
I’ve literally just got down to 0 ISO for the first time in months, so this reduction in max possible level is nothing to do with the ISO I have available. Sounds like a tech bug to me. Unless there’s some obscure rule about the sum total level of my roster or something, but if that were the case I would have thought many people would have found that before me.