Im not sure what is going on. I started a new project as a 2D side scroller and once in the editor created a new level and it works perfectly. Our logs mostly match except for those errors I pointed out and… this is one of the weird parts the compile errors at the end. I know those linker errors are because the engine cant the header files where the default classes are defined, but what I don’t understand is why your project compiles on start and mine does not… unless it is a silent compile and only lets you know if there is an error. The fact that it is happening on several different machines also raises an eyebrow. Incidentally, what version of Windows are you running? If it’s Windows 8 or 10 then it could be a Windows thing or a compatibility issue between Unreal and Windows.
If you go to the Unreal directory: ProgramFiles (x86) -> Epic Games->4.11->Templates->TP_2DSideScroller are there folders and files there? The files that the log is complaining of also look like packed files from a cab or other library and not individual files on your drive. For instance I do not have a /Game/… directory anywhere in my Unreal or Project files nor do I have a SideScrollerOverview.SideScrollerOverview_C file… But I do have a SideScrollerOVerview.uasset file in the Templates directory and if you view that file there are references to /Game/… directory so it has to be referencing a virtual file structure of some other large library file.
Since the launcher says your install is good and you’ve done several installs then it has to be a Windows permissions issue though I have no idea how that could manifest given that the engine is installed in a routine fashion.