FBX turns red at second export

Since 4.20, exporting the first time a fbx (from Max) as a static mesh works as expected, but as soon as I export a second time, the mesh is displayed with a red overlay effect (as if the mesh had red vertex color).

Thanks for your help.

Hi, thanks for your help!
The problem is mesh-side since when swaping the tree trunk material and (for example) the white rock, the trunk remains red. The third screen on the right is BaseColor only so I suppose this exclude any lighting issue (on top of that, unfortunatly light building fails (without any explicit message :().
Just in case, my project is a continuous migration since 4.14!