I am making a forklift, and I have a odd problem with the constraint (or I think it could be the constraints)
The forklift works fine when I want to take loads or move it, however, if the forks of the forklift touch the floor, the forklift start to move back.
In the next image, in the left, the vehicle is a btRaycastVehicle. Next there is a cube (call boom) with a hinge constraint to the vehicle. After that, there is 2 slider constraint, one to elevate the forks and other to move the forks (elevate constraint is between the boom and other cube (call base). The another slider is between the base and the fork.

In the right of the image is the case where the problem happens. The solver is the SI, constraints has 200 iterations, stepSimulation is called with 50 maxSubSteps and fixedTimeStep of 1.0/120.0 (fps are not a problem). The mass ratio between vehicle and boom, base or fork is 1:5 (so mass ratio boom:base:fork is 1:1:1). Forks has ccd activate.
Any suggestion what could be? (currently I am short of ideas to try D=, so any idea about what try would be nice)
Thanks!!