Thanks, @controlav. Actually it was your post from a couple of months ago that led to my question. Discussing your update to 11.15 you said
Although I only have three S1 devices left, it was the worst S1 update I can remember. Took ages to do (via PC), and once finished my Play:5s both needed forced reboots to be discoverable on the network again.
I replied that my own update went smoothly.