That is indeed a very weird issue. A few things that I’ve run into in the past which might help you narrow it down:
- Building from the engine will invalidate most files built by VS. If you are, stop using the “Compile” button in the editor.
- Compiling while the editor is already open will recompile a ton of stuff as it thinks you’re hot reloading.
I know these are less than helpful, but usually there’s a specific set of circumstances that causes your binary files to get invalidated. You said that just re-opening your project via the .uproject file is causing this… Can you reproduce this with a clean project? Does anything inside the .uproject file change in-between these runs (check the .uproject with Notepad)?
Again, these are just shots in the dark but it IS a very strange issue after all.