Collision mesh does not properly collide

[Fima2003]

Intro

Hi!

I am a graduate student at Technion, and I use MuJoCo for my research on picking up deformable objects.

My setup

mujoco 3.3.2
python
macOS Sequoia, M-series chip

My question

I would like to pick up a deformable object with UR5e robotic arm and a custom gripper. The gripper is created from 3 parts: left gripper, a hook on the left gripper to keep the object in place, and the right gripper. The issue I am encountering is that when I try to bring the grippers together, the hook makes a contact with something that is not a physical part of the gripper. the collision meshes tightly represent the gripper, so if anywhere the contact should occur its there. But as you can see on the video, it occurs before getting close to the gripper.

Screen.Recording.2025-08-27.at.11.14.35.mov

Minimal model and/or code that explain my question

Because for this model to be visible, one requires the assets, I have create a repo, where you can clone all the necessary files and experiment for yourself.

Thank you in advance!

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.

[quagla]

Closed as duplicated of #2826