Will not accept .doc filetype

This is a known issue that was introduced with WordPress 4.7:
The mime-checking algorithm was improved, but an unwanted side-effect was that other media types than image files fail to be uploaded.
A patch has already been committed to the development branch of WordPress, so this can be expected to start working again when WordPress 4.7.3 is rolled out.

In the meantime, there’s a plugin with a temporary workaround. That plugin should be removed once your site updates to 3.7.3.
More info here:
https://www.ads-software.com/support/topic/read-this-first-wordpress-4-7-master-list/#post-8521428

I have not had this problem with WP4.7.2 using pdf and docx file types. Whether the problem is specific to doc (or some other types), it is not the case the media replace is limited to image files.