All of a sudden my trusty 90's synth's MIDI sustain pedal is triggering my Micro Piano's lowest notes when pushed and released.
 
Keys are acting odd also.
Hold a key and it plays a sound (check).
 
Lift that key and it plays the sound again. (what???)
 
Tried it with a 2nd synth controller and it works fine.
 
Synths are routed thru a MOTU MicroLite.
 
[SOLVED]
MOTU MicroLite port 3 is bad. Moved the MP's IN cable to port 4 and all's well.
 
Only 4 ports to go.  It's only 5-6 yrs old with minimal usage.

Don't forget the midi filter plugin for filtering unwanted messages.

I'm guessing the port isn't actually bad, but something in the synth is telling it to change the key maybe? Just a guess.