Cubase Pro 11 & 12 Midi data not reaching Multi-timbral Synths if more than 3 tracks unmuted

Scan 3XS Scan Performance Audio 17" Laptop, about a year and a half old.
Windows 10 Pro
Cubase Pro 11 v11.0.41 Build 448
Cubase Pro 12 v12.0.20 Build 263
Various Soft Synths and plugins.
Steinberg UR22c Audio Interface (latest MIDI driver)
32 Gig matched Corsair RAM
Samsung 1TB 970 EVO PLUS - System Drive
Samsung 1TB 860 EVO - Project Drive
Samsung 1TB 970 EVO PLUS - Library / Sample Drive
High Power Sceme

If I insert any Multi-timbral soft synth such as Kontakt 6, East West Play 6 and have more than 3 MIDI tracks with Dynamics, Expression or Vibrato automation data unmuted and playing I get dropped MIDI.

If I remove the Dynamics, Expression or Vibrato automation data I can have as many MIDI tracks playing as I like.

This happens to any Multi-timbral soft synth only.
If I insert many instancies of Kontakt for example, with only one library in each, the MIDI with automation plays perfectly.

This indicates that the issue seems to be when multiple and constant MIDI data is being transmitted at the same time.

I know it is not audio drop out because, in Kontakt for example), you can see the MIDI channel indicator flickering and you can see when the audio is being played in the meters on the right hand side of each library and I can see the dropouts happening,

It does not matter which librarys I load in Kontakt as it happens to them all.
Remove the Dynamics, Expression or Vibrato automation data and all librays play with no dropped notes. The same for any Multi-timbral soft synth.

The issue seems to be that for some reason, Cubase is not passing the data to the soft synths.
I always use the following CCs.
CC1 for Dynamics, CC11 for Expression and CC12 for Vibratio
unless the Soft Synth requires some thing different.

This issue is in both Cubase Pro 11 and Pro 12 and started happening out of the blue about two weeks ago. No new windows updates, no new programs (except Pro 12), no new hardware.

The Laptop is a custom built DAW workstation from Scan Computers and came fully optimised for audio. I also went through ALL of the Optimisation suggestions on Steinbergs, Prosonus, Sweetwater’s webpages and a couple of others and there were only 3 tips that Scan had not applied.

Nothing is loading windows Start-up, usless Windows guff like Cortana, Games, Fax and the like have been uninstalled.

Latancy Monitor 7 (left running for an hour) reports no issues.
MS Memory testor left running over night and reports no issues.

Windows Task Manager & Resource Monitor show no issues, the CPU is not spiking and the memory use is low.
Samsung Magician reports all drives are fine, 2 have 100% life left and one has 96% left.

Cubase Audio Performance - peak, Real Time & Disk Cache run at around 25%. ASIO Guard fluctuates but never peaks.

Settings I have tried:
UR22c - Normally my Buffer size is 1024 Samples but I have tried it at 1536 and 2048 but made no difference
Cubase Advanced Options:
32 Bit Float (My default)
Activate Multi Processing - Unenabled
Activate Multi Processing - Enabled
ASIO-Guard Level, Low, Normal, High
Audio Priority - Normal & Boost

MIDI Port Setup:
Use Device “WinRT Midi” - ticked
Use system Timestamp for WinRT MIDI Inputs - Ticked & Unticked

When this issue started I created a blank Cubase Project in both Pro 11 & Pro 12.
Sample Rate - 48.000 KHz
Bit Depth - 24 bit

I inserted 1 instance of Kontakt 6 (I also tried Kontakt 5) load any 10 Librarys.
In this test I used Spitfire Studio Strings Violin Legato Patch.
Right clicking on the Instrument track I then added 9 midi tracks.
I then played in a simple legato line (no ensemble).
I drew in the Dynamics, Expression or Vibrato automation data .

Starting with all tracks muted, I unmuted each one until the drop-outs started.
3 unmuted play back perfectly
4 or more unmuted and the droputs start.

I then inserted 10 instance’s of Kontakt with 1 Legato libray loaded in each and 10 instance’s East West Play 6 Symphonic Orchestra with 1 Legato Violin loaded in each. On each of the tracks I have the same simple Legato midi + with Dynamics, Expression or Vibrato automation data.

All 20 tracks play back perfectly at the same time although ASIO Guard is around 80% but never peaks.
Although it works this is a messy way of doing things and leaves no room for Insert plug-ins.

On the same Laptop I tried the same thing in Studio One 5, Pro Tools 12 and Ableton Live Suite 11 and there is no drop-outs with any Multi-timbral soft synth.

Previous to this issue starting my cubase projects would have around 1- 12 tracks of audio samples, 10 - 30 Midi Tracks with 3 - 5 insert plug-ins and there was no issues at all.

From my testing, it is clear that it is a Cubase issue but no idea why it is happening?