Have you tried rebuilding your project?
[edit: This may or may not work depending on ones particular situation. All the files and folders deleted in step 1 will be regenerated anew, so if one of them had been corrupted for whatever reason and is causing a problem this is a quick way of making everything clean again. This probably should be the first thing you try before anything else.
Also, it’s wise to use some form of version control (like git for instance), that way in the worst case scenario you can always revert back to your previous working build.]
- Go to your folder and delete the .vs folder, Binaries folder, Build folder, Intermediate folder, Saved folder, the .sln file and .db file.
- Double-Click on your .uproject file and click ‘Yes’ to rebuilding the missing modules.
- Once the engine is open and all the stuff has been rebuilt, Right-Click your .uproject file and select ‘Generate Visual Studio project files’.
- Double-Click your .sln file to open Visual Studio which will then rebuild itself.