Whacheon WL580x2000 Shift Problems

I got in a Whacheon WL580x2000 from 1987 with very little use on it. Problem is that it only shifts though 3 gear ranges and not the full 6 speed ranges. It has a rotary crank speed changer which the folks at Whacheon tell me is only sold outside of the United States.. Gears are all in perfect shape and everything shifts fine if I remove the shift assembly and shift by hand. Obviously it is a timing problem with the shift gear assembly as one shift linkage goes through 3 shifts then the other shifter is supposed it flip the direction and then the bottom shifter can go through it's sequence again. The folks at Whacheon tell me that someone will call me back but after 3 calls to them I gave up. Anyone have a manual that may explain things? Any help is appreciated. Thanks, Marc