Amusing, but it's so preventable.
The updaters/installers use the OS file indexing to locate the existing version of an application. If you've turned off OS level indexing, for example Spotlight on a Mac, then the updater won't find the file.
This is an issue for all stand alone updaters. Note: the Apple store updaters use an Installer record created during the Apple installation process. They don't have to rely on the OS File Index.
So, not preventible when you turn off indexing on purpose, like we do for all our servers. Ha ha ha.
Still, that machine is indexed. hmm.
As a follow up the Mac Servers are doing delightfully well now that I used a FULL 14.4 installer.