2016-10-28 by ken@...
I've seen this problem, too! I first noticed it when using the IOS remote. I'm wondering if it's being caused when you have more than one remote communicating with to your piano and a volume change on one remote does not successfully receive and execute notification of the change - creating an out of sync issue . And then the volume is adjusted it again on the other remote.
I remember something about the software protocol was changed to optimize this communication protocol without the doublecheck and verifying all remotes were in sync before the I/O center made the change.
Does this ring a bell with anyone?