I had this issue in the past.
This is how I fixed it.
I selected the faulty assets and then right clicked and chose view assets in a new window.
Highlighted those assets and saved them to a CDP.
I then deleted the assets.
When I did that, it showed they were available for download which I did, and the problem went away.
What caused that?
I don't know. I thought it was something with my install that caused the problem.