I have recently upgraded to Cubase 13 and in playback my Jazz Guitar track goes into a different instrument. Stopping and starting lets it revert back but a few seconds later it goes back to the other instrument.
I assume this is a Virtual Instrument instead of an Audio Recording. If so the most likely cause is an unwanted MIDI Program Change message in the MIDI data. These are often found in downloaded MIDI files. The easiest way to find and delete it is to open the MIDI Part in the List Editor. If you don’t just see it right away, it is probably buried under the Note Messages which you can hide by using the filter checkboxes at the top.
