in that case the guess was correct.

reset each panel memory via the mixer with the sequencer play OFF to show the correct voices for that part for each section of the song i.e. each panel memory. Part is selected at the bottom of the mixer, sound at the right, along with pan, volume, the rest etc etc on other pages.

the panel write sets up the correct conditions at the start of the song, but is then overwritten during the song by the old information in the panel memories.

to multitrack using panel memories (a technics feature) the information in the panel memories will need updating throughout the song. multitracking is usually a midi file style of format, with one voice on each track, where you can cut and paste to your hearts content and only need to set up conditions at the beginning of each track.

another way of proceeding is to step record into each track and insert the voice change at the correct point.

the easiest way for you depends on how many tracks and your personal preference of working, and how much potential editing is envisaged.
let me know if I'm not clear...