Rowe R-81 Selector Logic

I have a r-81 that I will either let me enter selections and play, or
it will not. It often plays the first song that I select twice (at
the beginning and the end of all of my selections). From what I can
see from the service and parts manual, it is due to a falty selector
logic. Does anyone have any idea if this is the correct problem, and
if so, the best place to buy a replacement?

Thanks in advance,

Andy