It seems like since updating to 2016 I am getting the warning that SW failed to open the document for an unknown reason error. I open up the assembly file & make whatever changes that need to be made. Then I open up the drawings and almost every time the drawing fails to open with the included warning. I then close that drawing file & then close the assembly file saving the changes as it closes & then exit Solidworks. When I restart Solidworks & open up the saved assembly, I can then open up the drawing without it giving me the error message. Gets to be very frustrating & costly wasting the time I have to. It's also not specific to any assembly or drawing but just about every one that I've worked with.