Fatal error on launch

I updated my Unreal 4.9 to 4.9.1 today and since then am having lots of crashes and errors when using the software. One of the most common crash is this one:


When I make adjustsments to my scene I get this message. When I close UE and restart it will work. Looks like its missing a file or something. Any ideas what this might be?

It looks like once I delete and object from a scene, UE still thinks this object is needed for the scene and tells me its missing.

One of the ways to fix this is not just solely restart Unreal Engine but to delete the [SAVED] folder from the project.