I've had developer mode enabled, but have not modified the software using terminal. I certainly haven't used root access.

I've installed apps from non-store sources, but most of those are now on the store, with the same version number. Only ones I can really think of that modify the system are myMoves and a program that modifies the standby screen.

When I updated, it said installation failed, could not find "devtools memory" or something like that. Just assumed that installation failure was due to that, and I could reinstall that from Nokia source.