Strange update behaviour

I have two PC's, my wife's and my own, both upgraded on line from 8.1 Pro to Windows 10 Pro. The only difference is that my wife's PC is 32-bit and mine is 64-bit. Yesterday, my wife called me to say that something strange happened when she booted her PC and that it was now displaying a 'funny' screen. I went to see what was happening and found an Insider-like screen indicating that an update was under way. I left it to continue, went back an hour later and the PC had gone to sleep. When I woke it, the blue Windows logo appeared with the rotating circle of dots underneath but it didn't seem to move on. After five minutes, I decided to do a manual reboot and all seemed normal except for a notification saying that CCleaner had been removed as it is not compatible with Insider. What? Insider has never been installed on that PC. Winver confirmed that the installed version is OS build 10586.63.
Today, my PC updated to the same version, without any Insider screen and without removal of CCleaner. I guess I will just have to re-install CCleaner on my wife's PC and see what happens.
Is there any logical explanation for this difference in update behaviour?

I don't understand why I am getting absolutely no reponse to this perfectly reasonable question. Has nobody else ever seen this strange update behaviour? I've searched and have found nothing.
Surely someone has some ideas.

TopGeek said:

I don't understand why I am getting absolutely no reponse to this perfectly reasonable question. Has nobody else ever seen this strange update behaviour? I've searched and have found nothing.
Surely someone has some ideas.

Probably not, 10586.63 is not insider version any more. Look at Settings > Update & Security > Advanced Options and see if it's Insider version by some chance.
Almost every larger update proclaims some programs as not compatible, Ccleaner is not only one. Reinstalling that program usually restores functionality.

TopGeek said:

Thanks for your response. On my wife's PC, under Update & Security, Advanced Options, I see that there were six items updated on 13 Jan. None of them mention Insider and Get Insider Previews has not been selected. The previous version was 10586.36 and is now 10586.63. What I can't figure out is why the update was running with an Insider update screen, removed CCleaner "because it is not compatible with Insider" and yet still ended up with the non-Insider version.
As a reasonably technical user, I am completely baffled by this.

Really baffling, I could only guess as much as you. I have been insider since the very beginning, never on retail edition.