You were right about it having feedback linkage on the left side of the tractor, looking from the rear. However, there is no missing or loose linkage there. However, there is a limit switch that makes contact as full lift is approached and it looks as if the wire may be broken. I don't know what the limit switch is for except, possibly to indicate max up position. Don't know what happens if the limit isn't made.I believe it's all done internally on that tractor. It could indeed be the feedback linkage but it will require take the top cover/rockshaft housing out to inspect it.
Although, I was checking some pictures from the service manual and it may have a linkage on the left side of the top link mount. Looking from the rear of the tractor.
It doesn't move at all for a few maybe 10 seconds or so. Once it starts moving it comes to full lift in probably 5 seconds.How quickly does does it go up after you start it? Does it sound like its loaded up while rising?