Thank you for reporting!
This will be fixed in an upcoming update.
However, in the meantime, try downloading this:
https://files.catbox.moe/6uufcj.reg
It's a very small file that will alter one part of your save data that's causing the error. Once you downloaded it, double-click it and choose "Yes".
Hopefully, it will temporarily fix the issue. (Fingers-crossed)
If it indeed fixed the issue, all the dolls will reset their equipped cards. (As well as the order of the dolls in battle)
At this point, simply try to avoid equipping cards that have exact duplicates. (Ex. If you have two or more Nicole cards that are both Level 0, Dressed, and Regular-Breasts, avoid equipping it)
I suspect this is the cause of the error, and it will be fixed in the upcoming update.