Problem with normals of blend shapes imported from blender

Godot Version

4.7.0

Question

I want to turn a cube into a “stair” using blend shapes. I created the blend keys in blender and imported them. the video below shows the “wrong” normals of the mesh when turning into the stair. I think the problem is, that the side triangles collapse into a zero face in the end, which probably makes the interpolation of the normals wrong. I have no idea how to fix it. probably something in blender, maybe make the face super small instead?

tips welcome. thanks.

ha, that was it. I made the “collapsed” faces just very small and now it worked: