Objects not colliding accurately

I want to use Isaac Gym to evaluate two-finger grasps in simulation. However, the simulation currently leads to unrealistic behaviour where the gripper sometimes passes through the object after some initial resistance.
Here is an example of grasping a cup where the gripper does not stop on the surface of the cup. The rendering is of the collision meshes which seem to be fine.

I tried to change some simulation parameters (e.g. the dt and substeps) but could not figure out what to change to get to more realistic behaviour and accurate grasp evaluation. Is anyone familiar with this issue or could provide some pointers to possible fixes?
The code for reproducing the example shown in the picture with Gym preview 4 can be found here.

I think you need to use softer joints for the fingers. Because the surface is very thin, collision will allow penetration, with a distance based on how strong the force/torque is on the joints that pinch the fingers.

An alternative would be to make the wall of the cup thicker, if that still works for your use case.

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Thank you for your reply!
Could you please provide some pointers on how to achieve this/ which parameters to change?
I played around with damping/stiffness for the joints but could not get it to work - are these the relevant joint parameters or are you referring to something different?
Also, regarding the wall of the cup: I tried increasing the thickness parameter of the cup object but without any success.