A workaround of the stats problem on the dolls is to access their inventory by first starting from the inventory of one of the heros.
for example : Open inventory of DK, click in it to arrive to the Doll, unequip and reequip an item and you should, or move an object from the inventory and then you should see the changes again.
The stuck stats often occurs when you just summoned it and enter his inventory by clicking on doll and opening his own inventory ( you can open 1 inventory window by hero/doll )
At least it's what i could see by myself
