Eric,
Welcome to Beoworld !
I'm almost sure that the "alternative" speed is exactly the double of the normal, that is 66rpm instead of 33.
This is almost always caused by a slipping belt.
The motor will spin up too easily, it will reach a too high speed and
the electronics will happily lock it there.
There can be other reasons but a worn belt is by fra the most often seen.
We had other threads regarding this issue on similar decks but the
essence of it is the above.
Martin