Good to hear it works
Those old things often just need to be used to stay in shape. It may have been a bad contact at the switch bank.
The reason for my latter question was that on FM, the stereo light has a separate sense/control circuit that may develop a fault even if the audio part of the stereo decoder is working. I have a 900 myself that needs to be left on a stereo station for a while before the light comes on, although it plays in stereo right away.