Your problem is due to the shader used to render your preview. Hopefully, you can easily remove it.
Go to your Preferences and under the general section you should find the Material Preview Shader. Just hit the cross on the side and restart Substance Painter. Your thumbnails should look correct.
If you get lost, you can find a more explained answer to your question in the documentation.
Please, do not hesitate to contact me if your problem persists.
Have a nice day,
Cyril Dellenbach (Micro) | QA Support Artist | Adobe
It's possible that your bevels are not in the good folder. Bevels are normal maps and therefore should be in the Textures folder (Textures > Hard Surface > Base Shapes).
To locate your maps, right click on your asset > show in > show in explorer
If your Bevels are not in the Textures folder, please try to move them in.
Best regards,
Cyril Dellenbach (Micro) | QA Support Artist | Adobe
understandable but as I wrote above I created copied these materials in a separate folder and uploaded them to my shelf for quick access and as a consequence they lost icons
When you upload your copied assets, you need to upload them in the "Texture" folder of your shelf. Otherwise, the thumbnail won't be the proper one. Are your copied assets already in the texture folder of your shelf ?
Best regards,
Cyril Dellenbach (Micro) | QA Support Artist | Adobe
In your file explorer, go to : D:/ My SP resources to shelf
Here is the location of your shelf. You will see many folders with different types of assets (alpha, environments, shaders, etc). Yours are normal map, therefore you need to place them inside the texture folder. The thumbnails won't be correct until you place your assets in there.
Best regards,
Cyril Dellenbach (Micro) | QA Support Artist | Adobe
As you can see in your shelf folder (in the picture you sent me), the textures folder is missing. Add a new folder, rename it textures and move all your normal maps into this textures folder.
Best regards,
Cyril Dellenbach (Micro) | QA Support Artist | Adobe