Export physics from UE4 to Isaac Sim

I am trying to export my physics constraints from unreal engine to isaac sim, for instance, the limitation for an object to move to a certain position etc.

I used the provided UE4 connector to omniverse. And I used the default options for the exporter with “export physics data” checked.
Unreal Engine 4 — Omniverse Connect documentation (nvidia.com)

After the usd is generated, I tried using play in edit mode in unreal and isaac sim simulation to test my constraints. They all show different result from my original unreal map does. Is there something I am doing wrong? Or there is some way to test for physics in isaac I do not know of?

At the moment the only physics data that’s exported to USD is the collision data, no constraints.