I cleaned and reseated all the connectors. Found a sound board mounting screw lying
on the sound board. Screwed that in where it belonged. I checked page 1 of all the voices (selectable from the panel) and mapped the bad ones. (The bad ones slow down and stop.) I have them on an excel spreadsheet. Don't know how they map to the eproms though.

Another interesting symptom: All the rhythms (styles) work OK when only the drums are playing. If I play single notes with the right hand, the tempo slows down and after a few seconds I get a "Warning Too Many Events" message. It I start the accompaniment (left hand) it freezes immediately.