It's a bug. :)
Rolling back to an earlier version will fix it -
Start typing cmd on the Start screen in the task bar search field to find the Command Prompt then click Run as Administrator
copy and paste this line then press enter to drop back to the Sept 13 build
"C:\Program Files\Common Files\microsoft shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.15601.20148
Don't forget to turn off automatic updates for at least a few days, otherwise it will be reinstalled within a day. Microsoft is aware of the issue but I have not heard how soon it is expected to be fixed.