blender (2.93.4) FBX export animation trouble ("scale animation will be discarded")

I am just starting a project, and I can’t get Unity to import very simple character animations I’m building in blender.

I have an IK humanoid rig in blender.

I made a t-pose and built an avatar out of it.
I made a simple “idle” cycle, exported to FBX, and it imported just fine. It works on my character just fine.
I made a bad 10 frame sword swing animation, and it imported just fine. It works on my character just fine.

However, every time I try to make the sword swing animation better in Blender, and export it to Unity, I get errors like this:

7493404--922559--upload_2021-9-13_18-12-41.png

What’s worse, while the animation plays in the preview window just fine, it does not work at all when put on the character after these errors occur.

There are no scale animations on any bones in blender. I have tried everything I can think of. I even tried rebuilding the animation from scratch. It worked on my character for the first few iterations, then started throwing these errors and no longer works on my character. I’m not doing anything in blender but moving around IK bones and rotating a few non-IK bones.

Any ideas?

Ohh, and I tried to put the native blend file into the Unity folder… it imported, shows in preview, but when I tried to assign the animation to my character, Unity crashed.

7493408--922562--upload_2021-9-13_18-21-30.png

In case it helps, here are my very simple sword swing blend and FBX files

7493414–922565–problemanim.zip (286 KB)

same problem to me. still no answer.