The simulation result of MPM demo is not as expected

[Zhoufanghao]

When I run the demo of Hybrid (rigid-and-soft) robot in the Soft Robots Section, it occurs that the ball bounces away, and the beam seems to jerk for a while, which is not the same as what Doc's video shows.

ball.mp4

But other demos in the Soft Robots Section work well and can be reproduced.

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more information about my envs:
Win11 and WSL2, Running on [NVIDIA GeForce RTX 4090] with backend gs.cuda.
[Taichi] version 1.7.2, llvm 15.0.4, commit 0131dce9, linux, python 3.10.16, Starting on arch=cuda