If this is new behavior for MIDI files that have played in the past. I have had luck power cycling the Disklavier. Pull the plug and wait a few minutes If that fails, see if you can get another file format to play. Start with a PianoSoft file. If that works, then the MIDI files may be corrupted. That may point to a hard drive about to fail. I had to upgrade my to an SSD a few years back after the original hard drive failed. Took some time, but wasn't hard.