Starting from product update 1.0.23.0, you might encounter this error when attempting to terminate leases.

This is a product update aimed at splitting a previously used account into separate accounts for P&L.
This can be changed in the Lease Categories page:
Old Account
Old account HAS to be cleared or you will continue to receive that error.
Same Account
If you do not have practice of splitting Gain or Loss on Termination - these accounts can be the same.