It may not be a key balancing situation.  Some players activate
a key lock when the pedals are brought down (more likely it happens
when the pedal door is opened).  It's not difficult to disconnect
this feature, although sometimes you do have to remove a few keys
to get to the disconnecting point, and that can be an adventure
involving removing the upper stack assembly.

Other pianos have a manually activated key lock with a small lever
under the keyboard to lock/unlock the keys.  This one is handy in
homes with small, unmanageable children, or kittens.  :)

David Dewey