A833 gearbox 4th gear doesn't work

No hold on boys.
I have modded my box the same way, and its dynomite on my streeter.Notice the brass synchronizer rings are still in there. And the hubs are not modded. So its only half crash-boxed. As long as the brass is good it will be fine for street. You wont notice any difference, except it shifts like butter at 7200.
Now, I see one problem, the brass rings are sitting very low on the cones.So if the shifter over-shifts it will scoot those brass out to the end and the backside will pop out.
Question is why is it overshifting? Ima gonna guess it an early side-cover with the brass forks, and the interlock pin is missing or too short.The following test does not apply to the late-style roostercomb interlock cover.
Heres the test ; 1) lay the cover down on the bench, 2) shift the rear, 1-2 lever into a gear, 3) attempt to shift the front, 3-4 lever into a gear. There should be almost zero lever movement available.Maybe 1 degree.
If you have more, say 4 or 5 degrees, take the thing apart and either replace the interlock pin or weld it up to work.I suppose its also possible that somebody replaced one or both of the ball-bearings with smaller ones.They should be the maximum size that fits in the tube.

Oops, almost forgot. Before you do anything, check the back bearing for endplay.There should be zero. The test is to pry the geartrain back and forth. The output shaft should not move longitudinally. Its possible the bearing is worn out or the wrong bearing was installed in there. That bearing is special, so check it carefully.