Cubase 8.5 Shutdown/Restart Issue

Hello… first time been on one of these (although these forums have helped me in so many ways!!)

Anyway, I have 2 rigs - one Cubase computer syncs and prints into the other.

My writing is on the main computer in Cubase 9 (which also shoots to VEP on this computer and two others); the second computer runs Cubase 8.5 and holds video and surround reverbs for the incoming stems, eq and a limiter for the stereo fold down. I’m using 8.5 here as it is the last version that had video firewire out.

When I initially boot and load up in the morning, there is a crazy amount of crackling and staggering. Shortly after, the Cubase 8.5 print machine restarts itself and when I load up the Cubase 8.5 session again it is totally fine.

My systems are as follows:

Cubase 9 Machine - MacPro 2013 3GHz 8-Core Intel Xeon 35 - 64 GB RAM.
Cubase 8.5 Machine - MacPro 2009 2x2.26 GHz Quad-Core Intel Xeon - 12 GB Ram

(I also have 2 VEP Machines which are 2009 MacPros… don’t think they are the issue though. I also run VEP in the background of my Cubase 9 Mac (for the set-and-forget instruments)).

Both Computers:
El Capitan
HDSPe MADI 128 Channel PCIe (Cubase 9 machine housed in a chassis alongside an 8 core UAD Card - Cubase 8.5 machine housed within the computer itself)
I keep my MacHD, Session HDs and Sample HDs separate.

I was running ProTools 8 HD2 (TDM) on my print machine with all of the above firing fine in Snow Leopard (on the print machine only)… it’s when I swapped the machine over to Cubase this started happening. I still have the TDM cards in there as I go back to PT8 on a bootable drive when I have to.

I have a Big Ben Clock, ADI-648 and Apogee Ensemble (this one is on the Cubase 9 Machine) and a BCF2000 as a fader board for Cubase.

I’ve attached a few lines of code around the time of the weird restart just in case that helps.

SO… bloody mess that I hope you peeps can help me with!!

Thanks in advance!!