Do you happen to have a blueprint open after you save all? If you have a lot of inheritance going on and even though you have just saved, the blueprint being opened will tell the engine that certain assets are dirty.
I am having a hard time reproducing this error here, can you let me know what version of the engine exactly whether it is a compiled (from GitHub) or pre-compiled (from Launcher)? Also a copy of your DXDIAG would be helpful.
Thanks
Eric Ketchum