Rhino 6 WIP - texture on object becomes garbled when updating texture externally

unhandled
#1

I am trying to make my very first steps in material editing with Rhino, so please bear with me. I may do something wrong.

I am trying to use Rhino to visualize in 3D what I am editing in 2D in Photoshop.

I have loaded an fix file into Rhino 6 for Mac WIP, the file loads fine, all textures are properly assigned and in rendered view everything looks normal.

I then proceed to edit one of the assigned textures in Photoshop and the moment I save the file in photoshop the respective texture in Rhino becomes all garbled up.
I can also not reassign the texture in Rhino - the 3D model will then render complete black.

Only a complete reimport of the fbx file will render the updated texture properly.

Am I doing something wrong here or is this a current bug in the Rhino 6 WIP ?