I took the gear box apart and noticed that some of the gear shafts did not spin properly in the grommet caps. Either the the grommets aren't perfectly round or the shafts are lightly bent or not round. I found the perfect drill bit to fit the grommets snugly and cleaned it out smoothly. The shafts then fit perfectly and spun freely. This got rid of most of the stiffness I had in one gear box.

Secondly, I connected both gear boxes to a battery pack and let it run in one direction until the battery drained then crossed the wires to run the gears in the opposite direction on a fresh battery pack. I ran each direction twice on a total of 4 battery packs. Each running about 45 minutes continuously until dead.

I notice a big difference in the sound of the motor and gears after this break-in. I believe this help mess the gears much better.

I then installed the newly broken-in gear box and made sure that I did not have any metal or other wires making contact with the board.

Everything now runs perfectly. I ran the tank for about 30 minutes just to be sure.