Hi @RitchieFromParis ,
So sorry for any inconvenience.
Finally we have some good news to share that the real issue is identified with your problematic RC file.
The issue is caused by a specified board color set in the Preferences dialog -> General -> Electronics -> Color -> System Colors -> Board.
Screen Shot 2021-09-17 at 11.13.40 AM.png
The problematic color for the board is: Black=#282828, White=#dfdfdf.
The easiest workaround is to change the board color for Black and White to others, e.g. Black=#111111, White=#ffffff.
Screen Shot 2021-09-17 at 11.26.25 AM.png
And then reopen your designs in your account to check the CAM preview and 3D PCB, they should be OK now.
Our graphic expert is investigating this and we will keep you be posted once we have a fix about this.
Thank you so much for all your great help and patient.
Best Regards,
Helen
Helen Chen
Principle QA for AutoCAD Windows