Classic/Antique Car Repair: TR-6 gear shift, several different ways, shift lever

Question
I have a 1972 TR-6, bought last month. My first and I am in love. However,
the shifter has several times stuck into a "center" position, but actually stuck
in first gear, can move to 2-3 positions (feels like where 3 and R should be). I
take it apart and the shifter is stuck "above" the three channels, out of
position. I tried regreasing, stretching out the spring for more tension, set
the two pins in several different ways. The anti-rattle pin is now missing, but
it did this with or without. My TR mechanic is a bit stumped and it happens
after a long drive these last two times. I park, and when I return to the car -
first gear only, in a middle position....what makes it pop up and what can I
do?

Answer
Hi Ken,
That spring under the cup shaped retainer is very strong and I can not picture it allowing the shifter to come up out of the three rail slots, even on hard shifting. Look at the pins on the side that go all the way into the slots on each side of the shift lever ball to see that each is far enough in to engage the slots in each side of the the shifter ball. Also check to see that the end of the shift lever is not excessively worn and the the slots are not worn in the shift rails and that the bolts are tight that secure the slot ends on the reverse shift rail and the 1st/2nd shift rail. After doing this, lift up on the shift lever to see how much play the spring has.
It is also possible that one of the shift rails is moving too far thus allowing the shift lever to swing up and out of the slot.
It would help if you could figure out which position the lever is in when it comes out. Try shifting 1st to second and lifting on the lever to see if you can make it come out. Since you know it is stuck in 1st it is most likely coming out in the first/second slot.
Let me know if you find anything.
Howard