ROON constantly drops out/stops/starts and loses end point with both local library and Qobuz...

Roon Core Machine

Core - iMac 2015 QUAD CORE 3.2GHZ 1TB SSD 32GB RAM

Networking Gear & Setup Details

Total system wired SHIELDED CAT6 INTERNAL
All wall plates connections professionally terminated
Audioquest Carbon patch cables
Only WiFi device being iPad remote.
VPN/Dedicated IP is bypassed by ROON

Connected Audio Devices

2 Audio devices connected with only 1 ever in use

MOON 680D Ethernet Input [priority end point]
ZIDOO Neo Alpha Ethernet Input [secondary end point]
The ZIDOO outputs via USB into the MOON 680D via the USB input when in use.

Number of Tracks in Library

My library is exceptionally large at 800,000 tracks, 40TB on 2 external USB 3.0 HDD connected directly
to the iMac which connects directly to the Ubiquiti outputting to the end point/s.
Best Network practices followed.
I understand the size of my library is in the very small percentage BUT the remote is incredibly responsive and fast as is core performance, instant access everytime.

Description of Issue

The responsiveness of the remote controlling the core is very fast and file access is exceptional and immediate.
Navigating through menus either directly using the core or wirelessly with the iPad is snappy and never lags.
Accessing the library or creating playlists is always without issue.
Playback always commences immediately wether playlist, random, individually or shuffle this is either
on local library or Qobuz either individually as seperate entities or combined.
Seamless playback has never been available to me in my short time with ROON, it commences every time sometimes for a complete track, maybe 2 without incident although rarely then drops out briefly or at worse stops completely.
Commencing playback mostly works instantly before the same thing happens.
In addition the core loses contact with the end point.
I have removed my main drives swapping them out for a 5TB drive containing 25,000 songs with the same result.
I have power cycled all components including the Core and reconnected all devices during the course of said action.

The biggest positive I can add is my trial with Audirvana could not EVEN load my local library taking 3 weeks to import only 1 of my 20TB drives.
ROON loaded my complete library in 8 days.
Finally, up until now and for the last 12 years have exclusively used UpNP initially Twonky then ASSET with ZERO incident and fullproof usage 24/7.
I can still access ASSET to compare audio quality comparison to ROON if I can ever get it going!!
I am frustrated obviously BUT want nothing more than to get a result with ROON.
I feel it is within reach SO what am I doing wrong please community??