turn the worm gear to see if you can manually turn the shaft.
can you take another pic of the end of the pot with this removed.
this is the picture of the ring gear and the shaft.
the metal in the middle is the shaft connecting to the pot. there is already friction between the ring gear and shaft.
i checked, there is no gear slipping at all, so the only thing that can be wrong is the shaft and the ring gear is slipping. but it's pretty tight.
have you tried to power up the motor ?
spin the ring gear manual to see if the shaft turns and if it dose spin the 