Using svn trunk (revision 8513).
In ODEHingJoint::SetVelocity method SetParam is invoked to set the velocity. I think that SetParam is invoked with the parameters dParamVel and angle swapped. I've attached a patch describing the changes I made to get further.
I run into this problem when I was using the libgazebo interface from an external program (see bug#2924234). Trying to control the Pioneer2dx model through the position interface I got unpredictable results and behavior. After swapping the arguments as described above I got the expected results.