I would suggest that you try the latest (1.10) version of Panda3D, available via the “devel” section on the download page or via pip. I’m curious whether the issue also exists in the latest version.
If you think you’ve found a bug in Panda3D, please post a bug on the GitHub issue tracker containing a small reproducible test case that can be run without requiring additional files.
github.com/panda3d/panda3d/issues