Today I received a new MacMini bound to be a server for a small client. Came with 10.10.4.
N.B. For small clients (3-5 users), we install OS X Server, Filemaker app and Filemaker Server on the same machine.
Above that we dedicate the MacMini to FM Server only and get another MacMini for the rest.
installed, updated to 10.10.5.
Restart. Repaired privileges. Used Onyx to take away animations, ran through sys preferences to disable/set things etc.
Restart: everything worked fine and flawless.
Anyway: at this point, I wanted to update FM Server from 220.127.116.11 to 18.104.22.1682. Downloaded updater.
The updater started and froze on "27 elements to install". Of course, the server was closed, databases were closed, Safari with Admin console was closed, etc.
I restarted, same thing.
Then I restarted, but with holding down the shift key. Updater did its thing in 5 seconds, no freeze, no problems.
Restarted again, everything ok.
For what it's worth, posting it.