Tbg...I got mine about 1980. Not all Sony linear tracking tables had the "Biotracer" servo controlled arm, and not all "Biotracer" arms were linear tracking. Being an Engineer, I naturally had to get the service manual and see how this thing worked. Holy smokes! Working with balistic missile guidance systems I have seen a lot of schematics and block diagrams, but this Sony design is about as complex as anything I have seen. In fact, that is my only criticism.
As a have mentioned before, I became a convert to linear tracking after attending a High End seminar about the design and setup of pivoting arms. I concluded that there was no practical way to get all those forces and angles right across the recorded area. True, as you say, linear tracking arms have their own set of problems, but I think that I found one that did not have them.