Why the prefabs loose their preview in the Project windows ?

Suddenly all the prefab of my project loose their preview icon, replaced
with a blue cube.


I could instansiate the prefab in the scene then drag them in the Project windows
to recover the preview image. But i don’t know if they gonna loose again the icon…

Is there anyway to be sure they don’t loose the preview again ?
Even if they are send in a custom package ?

Thanks for any reply !)

Having the same problem today. It was caused because I moved the folder after importing. Solution: right click on the prefabs window an select “Reimport”.

Anyway to fix the prefabs if they all go black? I’ve tried reimporting

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