Following comment by @ Theo_Poilmek , it seems that the patch method is the reason.
In Physx 3.2 documentation it seems that default friction mode is not the accurate one and may create a frictional force up to twice stronger than the analytical one. There is need to change the Friction mode as explained here:
https://documentation.help/NVIDIA-PhysX-SDK-Guide/CoulombFriction.html