Sharpsville, PA
My TOM was similar to yours.
I believe that correct operation is to lock a ball for 'vanish' in the left orbit. Start Tiger Saw Multiball only on the right orbit... but that wasn't how mine always worked.
Right orbit shots are supposed to loop around fully, but mine used to sometimes take a bad bounce up top, and come to a stop in the vanish lock. If vanish is lit, I think the software counts it as a lock, which is how I would do it if I was writing the software. But the key point is that I don't think the post to divert the ball comes up when you hit the right orbit, only the left.
I also used to get Tiger Saw multiball starting from the left orbit somtimes (not all the time), but I don't think it was supposed to do that.
