I have been watching this topic from afar for some time now in the unlikely event that I got a win10 system. Being a relatively new and reluctant windows 10 virgin, there is no way I would have joined the insider program. What I have seen of the insider program in these forums, Microsoft should be paying users.
Getting involved in beta testing is a serious issue and when that relates to your OS doubly so.
My problem wasn't related to an Insider Preview issue since I was on a stable Windows 10 system.
I needed to do a clean install in order for the following update to finally succeed in installing:
Cumulative Update for Windows 10 Version 1607 for x64-based Systems (KB3206632)
Despite resetting the update process, that update always failed. It wasn't till I did the clean install on this computer
that it finally succeeded.
Since I was able to keep my personal files etc, I only needed to re-install the programs I actually use.
In the long run, it left me with a cleaner install. Next step will be a new Image which I can use should I ever run into this problem again.
(That update did install without problems on the system that's on the Insider Preview track.
)