We agree that you should guard against potential claims that items are missing if you open any safe deposit boxes and transfer their contents without customer approval, and we think your bank counsel is providing you with sound advice in this regard.
We do recommend that you review your safe deposit box agreement to determine whether any of its provisions also could be interpreted to apply to this situation. Also, we recommend maintaining records of all notices that you send out in case any issues arise later regarding any of the boxes transferred by the bank.