We are still investigating but for some reason UE is removing some files necessary to the dataprep.
Those dirty assets (with the stars) are missing in your plugin dataprep core
To get them back you will have to do a “verify” on your UE install in the epic games launcher
To not lose them again, do as @Antoine_Guillo recommends: after running dataprep they will be marked dirty, when you “save all” assets or quit unreal, Untick them and do not save those assets
