Forgive me if this is off-topic (for the forum) but I have spent most of this week's free time trying to resolve the issue.
I recently upgraded to "stretch". When I issued a "sudo apt-get update" after the upgrade I received the following messages
The hardware is a Pi 3 running as an always-on media server via Ethernet: wireless is disabled. The SD card shows 17GB free (using "df h").
It was necessary to "sudo apt autoremove". That said, it appears as though Sonarr, SABnzbd & Plex updated correctly.
Everything else (including access to the Internet) appears to be working correctly.
NB: I have similar issues after upgrading my Pi 2B.
Any assistance greatly appreciated.
PS: Both the official Raspberry & Stack Exchange forums were unable to assist, going so far as to say that a clean image should be used i.e. don't upgrade.