Python version of getjointvelocityvector() fails to return any value other than 0,0,0 on universal joints

I'm trying to run a simulation that requires information on the joint velocities for a universal (i.e. 2 dof) joint. Getjointvelocity works fine on 1 dimensional joints, however in the documentation its suggested we use getjointvelocityvector for universal or ball joints. Well i've tried but it doesn't seem to return any value other than 0,0,0 for my universal joint (which is quite seriously moving around).

Any ideas why that may be? Workarounds maybe?