Weird issue with shifting, Solved! Options

[914itis]

My shift linkage is well sync , no grinding at all and smooth shifting. All my bushings are new, shift rod cone screws are all tight in there .

Here is the issue.
If I am driving the car a bit aggressive, sometimes I would loose 4th and 5th, if I quickly move the shifter in neutral left and right (jiggle)a few times, they come back.

My guest is clutch cable adjustment or shifter itself.
Any ideas ?

[914itis]

Problem found ,
When I modified the shift linkage, I was a novice at welding, i still am. I inserted a smaller dimension metal pipe inside the factory linkage pipe (rod) first for better support then weld. The weld came loose and the only thing that was holding the shift bar was that extra pipe. If I didn't insert that pipe the linkage would be on the floor.

I took it to a professional welder today and the problem is solved.