The bone orientation was incorrect after exporting the .nif file, but importing a .nif file and then exporting it restored the correct orientation.

[Aquaman-N]

The model was exported without importing NIF before closing Blander.

After importing any NIF file, export the NIF file.

[Aquaman-N]

1.zip

Blander version 4.5

Interestingly, as long as the NIF file is imported and the blender is not closed, the skeleton can still be exported correctly even when other projects are open.

[BadDogSkyrim]

You're going to have to explain this much more thoroughly. Your top two images suggest one is using "pretty" bone rotations and the other isn't. Your last image suggests you're not using the latest. I really don't know what you're doing here.

[Aquaman-N]

You're going to have to explain this much more thoroughly. Your top two images suggest one is using "pretty" bone rotations and the other isn't. Your last image suggests you're not using the latest. I really don't know what you're doing here.

I did not enable "pretty" when exporting bone.

I have always used this option for exporting.

This is my import selection.

[Aquaman-N]

You're going to have to explain this much more thoroughly. Your top two images suggest one is using "pretty" bone rotations and the other isn't. Your last image suggests you're not using the latest. I really don't know what you're doing here.

I think I understand now. If you don't import the NIF file when opening Blender, exporting the NIF file will automatically perform "pretty bone" processing, even if this option isn't available in the export settings.

Since I created the physics skeleton XML using SMPRIgBodies in Blender, exporting it as "pretty bone" will cause my Y-axis and Z-axis to be swapped.

[Aquaman-N]

You're going to have to explain this much more thoroughly. Your top two images suggest one is using "pretty" bone rotations and the other isn't. Your last image suggests you're not using the latest. I really don't know what you're doing here.

Sorry, I reverted to version 22.2.0 after discovering a bug, and forgot to switch to the latest version to take screenshots.

[Aquaman-N]

You're going to have to explain this much more thoroughly. Your top two images suggest one is using "pretty" bone rotations and the other isn't. Your last image suggests you're not using the latest. I really don't know what you're doing here.

test.zip

I'm so sorry to bother you.
Version 25.14.0 will still automatically run Pretty Bone even when Pretty Bone is disabled.