Not here much as all my Volvos are gone, but saw this and had the same issue with my 93 940.

Take seat out and get the power seat module from underneath, pop the cover and reflow all the solder joints, or alternately, find the 1 or 2 cracked joints and resolder. I just reflowed anything that looked suspicious and bingo it did the trick, the seat worked fine. The memory was still dicey, but it went back and forth and the seatback adjusted fine until I sold it years later.

Mike