session and startup doesn't change sessions

[jimwg]

Greetings:

XFCE Mint 18.2 64bt.

Since upgrading from 17.0, Mint doesn't prompt for save session on logout. Does show display chooser on login but without session image icon as previously
had, and there's no switch or difference of session no matter which I select -- it's all the same.

Aside, I am wondering whether, as wildly suggested by a linux user, whether issues like this and those as Update Manager refusing to install security or other updates is because somehow far down the app and system files chain a critical file's permission got switched or changed so it derails the process. If this is a possibility, is there (I'm putting this badly I know) a kind of "normal file state template" out there that can run through system files and match and see whether permissions and such are properly set? Just a wild desperate notion that might help people from having to resort to full re-installs unnecessarily.

Thanks for any suggestions to track this down.

Jim in NYC