Stalling Motors

My team is using a grabber design as the scoring mechanism. It’s essentially comprised of two towers with high torque gearing and three motors. A pic of one of the towers is attached. Each tower has a connected full-length c-channel that has the grabber module attached to it at the end. After a few trials and scoring it seems to be like the motors on the tower stall out and it just gives up. There is enough torque and power to hold up three stars at a time so I don’t know what is causing the stalling. I need help with isolating the problem. I think it may be the movement and jerking of the arm going up and down that is causing resistance to the motors which lead to stalling. Could it also be a power issue? I’m running the robot on 12 motors.
robot tower.jpg

Where is the pic?

I edited my post. You can see the pic now

Stalling usually happens because of:
Friction
Weight
Lack of rubber bands
Bad gear ratio

Make sure the gears are aligned well, and also try to make it a little more compact.

Could there be an issue with power distribution?

Maybe, I would suggest putting one half of the arm on ports 2-4 and the other half on 7-9. Then run the arm only and see if it stalls, as that should be able to output plenty of power.

I can see that your tower do not go up straight, this might be the issue.

I would suggest that you first try adding a lot of rubber bands to the lift and if it is still not preforming then a switch from a 1:5 to a 1:7 might be necessary.

Make absolutely sure all of the motors are actually running and doing so in the correct direction.

Also check to see that the spacing is not too tight between the towers. This is major cause of friction. It also looks like there isn’t a lot of support between the two sides; more bracing will ensure that the two pieces of metal are parallel, which is also very important.

I don’t see any at all.

With 6 motors a 1:5 should be plenty.