Plex app non-functional since OS Reboot of ReadyNAS 204

I've been having issues with my ReadyNAS 204 for the past 2 weeks now - I resolve one issue and another one pops up!

I am using the latest firmware 6.6.1 and these issues appeared 'out of the blue' - unrelated to me upgrading either firmware or any of my apps.

I primarily use my ReadyNAS as a Plex server and the only active apps are Plex (for RN2xx), PlexPy and Transmission.

Initially, about 2 weeks ago, I suddenly was locked out of the online Admin page. My password had not changed, but all of a sudden it was not being recognised. The login panel would pop-up repeatedly and would finally dump me into the Password Recovery screen. I would answer the security question, but I would be told it was incorrect (which it clearly wasn't).

Throughout this time Plex and Transmission functioned perfectly (although I couldn't add new content via the Admin page). My shares and data were all accessible via Finder (I'm on a Mac with 10.12.4 Sierra).

After searching the forums and exhausting other options I performed an OS Reset. This obviously returned my username and password to default and access to the Admin Page was restored.

I thought that that was the end of my problems, but now I found that the Plex app (which was working just fine before the OS Reset) would no longer work. Further reboots had no effect. Toggling the app off/on did nothing. Attempts to upload the most recent Plex app failed (I'm currently on version 1.4.2.3400-ab906953b which is very recent and had been working fine).

RAIDar diagnostics shows "no errors found" but on occasion when I attempt to turn on the Plex app I will get a "bad NML call" error.

I've trawled through these forums for a fix but I'm still at a loss. These issues happened spontaneously and are not related to me doing any mucking around with the system, so I'd appreciate some assistance from Netgear in getting this sorted.

Thanks.