HingeConstraint lagging behind moving object

I’m experiencing an issue where a welded model hinge constrained to a moving arm lags behind the arm movement.

I’m creating a theme park ride where a big arm rotates vertically with two carriages attached at the bottom, these carriages should be able to rotate freely.

This video shows the problem:


As you can see, the carriages float around the area where the arm is rotating, while they should be solidly attached in position but still be free to rotate.

Any help is appreciated!