Headlight Motor

I have a 1984 vette with headlight motor problems and I hope someone can guide me to a solution. Several months ago I switched from plastic gears to the bronze gears in the motor. Since then the motors some times get stuck open, but you can hear the motor working (straining ) to close the doors. I can push on the open door sometimes to get it to close, but it is getting harder to do that. Is it time to replace the motor or go back to plastic gears. Don't want to waste money but I do want reliable operation of headlight doors. Any help on this issue would be greatly appreciated.