Rigid Body Constraints "Generic" connection

I don’t usually ask for help, but I am at wits end. When I connect two rigid bodies with a rigid body constraint, the physics goes crazy after it turns a certain amount. What I did was:

I Created 4 objects. Two rigid bodies. One static, the other dynamic. The third object is the RBC. The fourth RB is the one that is going to fall and rotate the mechanism.

I connect the two RBs with the RBC set to Generic. Then enter all the values, all zeroes, freeing the Y axis rotation, so it can turn.

Here’s the blend:

I’ve made RBC stuff before without problems. Maybe I am missing something now.
Any solution or advice will be appreciated.

Start position:

Everything rotating like normal:


Physics going crazy: