An investigation by Ed Bott casts doubt on KB3xxxx being the problem, and points instead to an Office update that affected Office 2010, 2013, and 2016; the Windows 10 update still affects Edge, Outlook, and File Explorer. We stand by what we said about the model Microsoft is using. The original article continues below.
Microsoft’s latest Windows 10 cumulative update, KB 3124200, dropped last week, but clearly needed more time to bake. While initial reports suggested that the update would fix some issues with WiFi connections dropping out, the latest cumulative update is causing some significant problems.
Reports indicate that in at least some cases, KB 3124200 nukes all Microsoft Word customizations, including custom templates, AutoText, macros, envelope addresses, autocorrect, and AutoFormat settings. It also reverts any custom spell check options you may have stored. The problem is serious enough that Microsoft has published its own KB on fixing the issue, KB 3129969.