I have a Rosegarden file with 2 MIDI segments. I assign e.g. the vibraphone to the 1st segment and the guitar to the 2nd one.
When I start the recording, the 2 segments are played with the piano instrument instead of the vibraphone and guitar.
The recorded wav file shows the same result, the piano has replaced the assigned instruments.
The workaround I found to get a correct recording is to play the composition before recording it. When the composition is played, the piano replaces all the instruments at the beginning for a short time, and then the right instruments are played instead of the piano. After that, the recording is OK.