1. Go to your Epic Games directory with Windows Explorer. It's usually C:\Program Files\Epic Games, unless you originally installed to a different location. Mine was on drive D.
2. Find the game folder you want to reinstall (get working) and rename it. I just put an underscore in front of the original name. ex. _ShadowComplexRemastered
3. Start the install from the launcher. It will ask you to "Choose install location". Select the base Epic Games folder where your game files are already installed. ex. C:\Program Files\Epic Games. It will then show that path and add the game folder to the end. ex. C:\Program Files\Epic Games\ShadowComplexRemastered. Click Install.
4. Let the Launcher download a couple MB's and "Cancel" the install, but leave open the launcher. Now you have a nearly empty brand new game folder in your Epic Games folder.
5. Go back to Windows Explorer and rename the brand new folder to anything else. Then, go to the original folder you renamed and name it back to it's original name. You can delete the newer empty folder.
6. Go to Launcher and click "Resume". The launcher will immediately Verify all files and you'll be ready to play.