Disparity map colors keep changing when using stereo camera with OpenCV

Hello,
I am a beginner in OpenCV. I am trying to generate a disparity map from a stereo camera and then reconstruct 3D. However, I found that the colors of the disparity map keep changing over time. I have already ruled out the influence of lighting conditions, but the problem still exists.

Screencast from 2025-08-23 15-53-01

Could you please explain what might cause this kind of variation, and how can I eliminate or stabilize it?
Thank you!