If you weren't aware, Microsoft is dropping support for Movie Maker 2012 as of January 10, 2017. While the programs will continue to run on systems where Windows Essentials is already installed, it's unlikely you'll be able to reinstall the programs if you are having issues. Obviously no further updates will be forthcoming (even if security issues or defects are found).
Before the deadline, you should definitely save a copy of the offline installer for your language just in case you need to reinstall Windows Essentials.
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Microsoft has given the vague statement that
Movie Maker will soon be available from Windows Store for Windows 10 users. But so far I've not seen any actual announcement of what that may be. So far I've only seen less powerful apps like
Movie Moments in the store without any viable replacement.
Update: Under the question about Recommended Alternatives, Movie Maker is no longer listed. This seems to confirm that Microsoft has no immediate plans with respect to a new Movie Maker.
If any of the Support Engineers in these forums can escalate this question, we'd all like to know specifics on what that replacement will be and when it will be available. Please reply before the deadline.