Thank you very much for the tip. I had never thought of changing the button that was set to sleep!
I did not have to use it with the update because the PC restarted as usual without asking for a...

This MAY BE the REASON why the download got stuck...

Last night, windows defender downloaded fine, but Cumulative Update Version 1607 for x64-based Systems (KB3189866) got stuck at 95% like it did...