Well, last year [0][1] consumers weren't able to have changes to the defaults. Well, some apps would change, but others wouldn't.

However, you can get the impression it happens more regularly because when individual default apps, like Photos, get updated (or if there is a problem in the registry) they may reset the association for the files they expect to handle.

[0] https://wccftech.com/windows-10-bug-unable-apps-defaults/

[1] https://support.microsoft.com/en-us/help/4467682/windows-10-...

Somehow it seems to do some braindead syncing when you set up a new device. When setting up a new laptop suddenly my desktop task bar switched sides to match the change on the laptop, and files stopped showing extensions (even though that wasn't touched yet on the laptop, the default is not to show them and that somehow seemed to carry over to my desktop).

Literally today it opened a PDF file with Edge for me. And, of course, file association page does not have a searh box to help find .txt among hundreds of useless and unassigned extensions.

See: https://devblogs.microsoft.com/oldnewthing/20170517-00/?p=96... for an explanation.

"A customer reported that each time they restart their Windows 10 PC, the file association for PDF documents keeps getting reset to the default, which is Microsoft Edge. [..]"

This is not a case of Program X messing with registry. This is the user explicitly setting Program X to be the default application.

I guess there is no way (given the current registry design) to differentiate between the user modifying the registry and a program modifying the registry.

Again, coming back to the original message - the case scenario is not that some program is changing the preferences. It the user changing the setting, and Win10 silently discarding the user input (after a reboot or some automated update).

I see it on every large update (like 1909) or so.