I've noticed the same bug, here's a more detailled description:
Description:
Apparently, every pet is supposed to improve "Accuracy" by 5, when equipped in the inventory Slot "Pet". For some pets, the accuracy Bonus isn't removed though when unequipping the pet. The following list is incomplete, because I don't have all pets yet.
Pets that work correctly:
-Beagle Dog
-Black and White Cat
Pets that don't work correctly:
-Black Cat
-Black Hound
-Calico Cat
-Yellow Lab
Steps to Reproduce the Issue:
Equip one of the pets from the list above in your inventory slot, remove it and equip it again.
Workaround:
Equip one of the working pets from the list above, to set your accuracy back to its correct value.