I noticed that the update takes a long time, and when the screen sleeps, the wifi connection disconnects and the installation gets stuck. 1 - I disabled the screen sleep from battery options https://mackeeper.com/blog/prevent-your-mac-from-sleep/ 2 - I cleared the cache from ~/Library/Caches, 3 - Restarted the machine and tried again. I left the update overnight, internet speed is 100Mbps but still takes hours for update/install. In the morning I found the latest version installed. Hope this helps.