I think the bug came from me moving the material files to a different folder (not sure).
As you can see in the clip, after deleting the object, the material returned and I could interact with it.
After that I need to change each material path to it's new folder for it to show correctly in the viewport.
p.s.
Is there an option to update the folder of the material automatically (by main folder material) instead of separately updating each node?
You had the node tree pinned. This causes it to remain in the Shader Editor, even if you select an object with a different material.
I am a little unclear on what the problem is -- if you are talking about re-opening each texture, then yes, that would be expected: you've moved the files, and Blender can no longer find them. You can, however, automatically search for missing files: File -> External Data -> Find Missing Files
Thanks Fen, I didn't know it was pinned.
About the "re-opening", I know it's expected.
Just wondered if there's a better way of doing that, like just pointing a folder and blender will refresh all the nodes that were selected, or something like that.
Closing the ticket since this is not a bug.
Problem was due to pinned node tree. Feel free to comment or reopen the report if different issue you were trying to explain