It is extremely common for these pins to walk out of the shift forks and even the shift tower. Replace them with these high quality German made spiral spring pins. Don’t settle for a thin wall parts store roll pin on your transmission.
With a dab of loctite you can further improve holding these fork pins in.
We have a handy 6 pack here, that will let you replace the shift tower ones and all 4 shift rails or have one or 2 extra depending on your trans.