Vipar,
Please right-click in the Content Browser and make sure that you’ve selected to ‘Fix up all Redirectors’. If you’ve already done that, please make sure that your blueprints and levels do not call for any assets that you have since deleted from your project. I’d also suggest that deleting your Intermediate, DerivedDataCache, Saved folders from your project.
Let me know if that makes a difference, thanks! 