in a ragdoll post almost 2 years back now ( here ) DYC wrote:
"First of all phcon_getposition returns weird results if you create more than 5 hinge constraints"

I have more than 5 hinge joints and I am getting similar behavior.
phcon_getposition sometimes sets vecParam1[0] to -2097152 which interestingly is exactly twice the range of a var.

Any ideas on what is causing this?