Hi, all. I had this problem in UE 5.1 with the Lyra project.
The solutions above did not work for me unfortunately, but if all you want to do is stop the editor from nagging you, just go to
Editor Preferences > Advanced > Data Validation > Validate on Save
and uncheck that box.
Doesn’t really solve the problem, but it sure is nice to save my project without being harassed by the editor.