Flex, Physics Constraint and Unreal Engine 4

I am using ue 4.20 and flex from gameworks
I made a packet using Flex cloth. But I ran into a problem. Flex particles don’t want to interact with ordinary objects in the world. When I move a package onto a cube with a physical simulation, the package cannot move it, although the package reacts with it, it bends, and so on. I have a capture tool for this package. In theory, the shafts spin, grabbing the bag, and when the bag pulls too tight, the shafts should stop. I set them max limit of power. But due to the fact that ordinary objects ignore flex, shafts do not want to stop.
How can you make objects react with flex objects and make them to move?

Here is my question on ue4 forum with image of my capture tool.
https://answers.unrealengine.com/questions/924263/flex-and-physics-constraint.html