Same thing just happened to my A4 on track 4. Pressing C on keyboard was playing a B flat. Other tracks were fine and correctly played C when C was pressed.
I tried clearing out all tracks, kit, and even creating a new project. I then tried running calibration. Nothing fixed it until I stumbled across this thread and decided to try the suggested fix here power cycling the device without USB connected.
Seems like it worked, and now all four tracks are back to playing correct notes. Really weird, hope it doesn’t happen again!