PossibIe rotation offset bug in GLB/GLTF armature export

[MrJoshBowman]

What are you trying to do, and what do you expect to happen?

I've been testing the armature export option for GLB files a bit, and unfortunately posted a hasty bug report for an old version, but this time i seem to have found a possible actual bug when exporting from the animation editor:

When on any frame in the 'Animation' screen, and rotations are keyframed to start in a rotation other than the pose default, the animation for the animated objects seems to be exported with the animated starting point as the default rotation value and then the animation is offset again over the top of that as if the default pose rotation is starting at (0,0,0).

What happens instead?

If i go back to the 'Edit' screen before exporting the animation to GLTF/GLB as armature, then the 'origin' rotation is set to the default position that the model resets to when in edit mode.

If i then go back to the animation editor, scrub the timeline to the first keyframe and export again, the 'origin' rotation becomes the rotation of the first frame and then the animation plays starting from that offset in the exported GLTF/GLB file.

I've attached the BBModel file, and two GLTF files generated (one from the Edit screen and one from the Animation screen) in a zip to hopefully clearly show the issue:
offset origin example.zip

Here are two examples of the first frame of animation for 2 GLTF files exported from the same BBModel file;

When exporting from the 'Edit' screen this is what the first keyframe in the exported animation in the GLTF looks like.

When exporting from the 'Animation' screen and the timeline is set to 1, this is what the exported animation in the GLTF looks like.

Model format in which the issue occurs

GLTF/GLB

Blockbench variant

Program

Blockbench version

4.9.4

Operating System

Windows

Installed Blockbench plugins

No response