Bootcamp operating system missing error after resizing partition
Firstly - Sorry for bringing up an old question - I just spent a year trying to find the answers and only found questions so I figured I'd answer a past one with my solution

Resize Bootcamp partition:


Boot to MacOS and use disk utils to shrink OS X partition leaving unallocated space on hdd


&lt;-- I believe you are at this point based on the empty space starting at 852326800 -->


Boot to GParted and use the copy/resize function to expand the windows partition to the left (this covers your extended space)
Boot back to OS X and use FDisk to mark the Bootcamp partition as bootable (Was partition 4 in my case and looks to be in your case)
Bless a Windows bootable USB before restart (with startup repair avaliable on it)

sudo bless -mount "/Volumes/**mountedusb**/" -legacy -setBoot -nextonly

Boot to windows usb and run startup repair
Restart and you should be good.