The problem is that the repair option only repairs 3.0.4.2
Instead of the latest version.
Maybe I'll run the msvc-2015.zip separately and see if that works.
Update: imsvc-2015 was an incomplete install from the last downloaded version of it.
I'll just uninstall and re-install the msvc-2015.
It turns out an error can cause the install to stop and thus further prevent attempts to install.
(Side note: it helps to reboot also to stop any incomplete scripts)
Raptor29aa's post in Install help was marked as the answer