Most of the pins I'm familiar with have a short knurled section at the top, which is supposed to swedge into the diecast shift collar. Once the collar wears enough for the pin to get loose, it's almost impossible to keep it secured. I'd suggest a drop or two of red LocTite on the knurl, or JB weld, if it's really worn at the knurled area. Just don't stick the shifter to the pin, as it needs to pivot there.
Jerry

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