1970 A833 issue jumping out of 2nd gear

I used to re-build transmissions for a living back in the 70s/80s. I have NEVER seen this problem, (outside of a neutral-gate adjustment) that could not be traced to one these things;
1) lack of proper or sufficient detenting or
2) clutch teeth worn off at an angle.
3) a long, heavy, shifter not centered over the shift mechanism.

> Once this starts it will never go away and just progressively get worse. But no matter how bad it gets, I have always been able to repair the parts as necessary.
Furthermore;
>That Pistol-Grip is not helping. The heavy handle puts pressure on the detent spring, just begging it to jump out; you may have to increase the spring pressure.
The later style (71-Up) sidecover has a better system to deal with that.
>If it still jumps out of gear, with the 71-up cover; the trans will have to come out, come apart, the clutch teeth back-cut, and the slider cleaned up.
I have successfully done this dozens and dozens of time on A833s and hundreds of times in General.
I have not replaced gears or sliders on my own transmissions for about 50 years; or thereabouts; I just keep repairing them; NO, not the same trans lol.
If you do take it apart, and you have the late-style sliders, I recommend to double up the strut springs, if you have spares..