The bell crank shafts on the Pro4 SC10 / MT10 are 5 mm plastic rods that seem to have some support at the top but the amount of flex tells otherwise. I took out a caliper and verified that the screw heads have a sloppy fit to the holes below the main chassis.
A simple and cheap fix: heat-shrink tubing to thiccen them up!
This probably doesn’t solve an actual problem but feels good to know it’s there.