Soundbank problem on Ensoniq SD1

My SD1 has 3 60-sound banks which you should be able to choose independently and
assign to up to 12 tracks. Using any of the sounds from one bank is no problem, but if I
try to add a sound from a different bank (using a different track of course), the other sounds
immediately convert to the new soundbank sounds in the same position as the new sound.
In other words, the 60th sound in bank 1 will change to the 60th sound in bank 2 regardless of which sound I choose in bank 2. I’ve checked midi settings to make sure I can either use local sounds or as a controller. I live in Atlanta and would be glad to take it in if I knew anyone who worked on a 30 year old synthesizer.