Forced account sign in and server could not be found

Server Version#: 1.13.4.5271-200287a06-x86_64
Player Version#: 6.16.1.4533

Hi all, I’m hoping someone can help with my Synology server/Android TV problems.
I upgraded to the latest version of Plex for Synology mid-March 2019 (Which would have been Plex Media Server 1.15.1.791). Up until and including this point I hadn’t created a Plex account or logged into the server/player with a Plex account.

I noticed that once I had upgraded the server, Plex on my Android TV won’t see the server running on my Synology NAS.
I tried all sorts of network and permission changes, but no luck.
The Plex account log in screen was missing the skip link and was forcing me to log in to somehow see the server, so I created a Plex account and logged in and it worked straight away.
Sigh.
I don’t need to access my Plex server remotely and I’m only connecting to the server locally via the Plex app from my android TV. No other devices.

So, I uninstalled Plex Media Server 1.15.1.791 and rolled back to Plex Media Server 1.13.4.5271 and rolled the Android TV app back to 6.16.1.4533, logged out of my Plex account across everything and cleared my cookies and low and behold it found the server from the TV again without logging in and I could access the server settings again without having to log in.
I added access from the local network so that the TV could access the server without authentication as an extra measure of not needing a Plex account.
Basically it worked again without friction as it had in the past.

I turned off auto updates for the server and TV and thought that would be the end of it.
Until last week when the Plex app on the TV couldn’t see the server all of a sudden. When I tried to view the Plex Media Server settings via the web interface it was forcing me to log in again. The only problem is now its saying server not found. So I can’t view or change any of the server settings.

This would all be understandable if it just didn’t work and the server couldn’t be connected to, as Plex reports it, but that’s not the case.
The standard Video app on my Android TV can connect to the Plex media server, browse the contents and play media without any restrictions. The same was the case when the Plex app claimed it couldn’t connect to Media Server 1.15.1.791 and again now it can’t connect to Media Server 1.13.4.5271.

Why can a non native media app on my TV seamlessly work with the Plex server when the native Plex app fails without reason?