On my work PC, I constantly get messages that "[Program] caused a problem, the default app has been reset to Microsoft Photo Viewer" etc. Then, when I change it back manually, Windows simply outright ignores it. Default apps on Windows 10 are a disaster, and I don't see the motivation for doing it. Why does Microsoft care which photo viewer or browser I use?
You might have been hit by a bug involving KB3135173 [0]. A later update fixed it, or modifying the Registry can fix it. Windows 10 seems to have issues if it expects a registry entry to exist, and it doesn't. (You probably have no control over any of this unfortunately, being a work PC).
