Is it too late to revert back to the previous Insider build to see if this one is the cause, or was that build 18363 ?
In any event, see if those cmds will resolve the Office problem but report it to Microsoft.
It's fortunate that you didn't experience problems after running WR on an Insider build because which each Windows Update, the Permissions change, which is why Shane needs to keep updating the program.
It's been found that running an older WR on the latest version of Win 10 has caused the machines to fail to boot after the reboot.
When there has been a Windows Update, it's best to wait until you see if the program gets updated before running WR but those two cmds can resolve most OS problems.
An additional one to run first is -
dism /online /cleanup-image /startcomponentcleanup
That one cleans out obsolete updates from the WinSxS folder, although older updates in Win 10 are supposed to be deleted after 30 days.
Depending upon what is wrong with the machine, that cmd can help.