Dresser Dozer gear shifter pushes itself forward

I have a Dresser TD8G Dozer that runs very well. I recently replaced one hose from the shifter valve body to the transmission. The next time I used it it worked fine for about 5 minutes and then the gear selector started popping out of gear into neutral. After another five minutes, the gear selector started being pushed back toward and into neutral as soon as I put it in gear. After being in neutral a few seconds, I could pull it into gear and it would go for a few feet, so i took it over to...

Dresser Dozer gear shifter pushes itself forward

Dresser Dozer gear shifter pushes itself forward