I’m not reproducing this behavior. I see this after exporting it the second time.
The problem is that the UVs are not being exported. By default, the exporter does not export unused UVs (though I noticed we are still exporting the buffers, @Guillaume_Pelletier maybe you can check this?). There is an option to export the unused UVs in the exporter code, but it is not currently available as an option the inspector UI. Maybe we can add one.