Rotation for thumb animation clip is only working in one axis in Unity, but works fine Blender

Hello, I have a humanoid model created in Blender and rigged using Rigify. I had everything working for a few weeks now and then my thumbs started only rotating on one axis in animations imported from Blender. I cannot figure out why. Has anyone else seen this? I've Google'd a lot and have yet to find a solution.

Video showing example of this behavior: https://youtu.be/hNurZm-4yXE

The screen on the left shows the import into Unity only moving in one axis for the thumb. NOTE: The other fingers work fine. The screen on the right shows the rotation in Blender working correctly.

Here are details about the rig setup, export and import.

Rigify Bone parent mappings: thumb.01.L parent is MCH-thumb01.L DEF-thumb.01.L.01 parent is ORG-thumb.01.L DEF-thumb.01.L.02 parent is ORG-tgumb.01.L DEF-thumb.02.L parent is ORG-thumb.02.L DEF-thumb.02.L parent is ORG-thumb.03.L

Blender Export Settings FBX version 7.4 binary

  Main tab
 Selected Objects checked
 Scale 1.00
 Forward: Z Forward
 Up: Y Up

     Armature and Mesh ONLY selected
     Everything else default

 Geometries Tab
 Apply Modifiers unchecked
 Everything else default

  Armatures Tab
 Only Deform Bones checked
 Add Leaf Bones unchecked
 Primary Bone Axis: Y Axis
 Secondary Bone Axis: X Axis
 Armature FBXNode Type: Null

 Animation Tab
 Baked Animation: checked
 Other checkboxes unchecked
 Sampling Rate: 1.00
 Simplify: 1.00

In Unity Rig set to Humanoid

 Left Hand configuration
     Thumb Proximal mapped to: ORG-thumb.01.L (Transform)
     Thumb Intermediate mapped to: ORG-thumb.02.L (Transform)
     Thumb Distal mapped to: ORG-thumb.03.L (Transform)

Thanks in advance for any suggestions.