The only difference is that last week I had an Ultrastudio 4K running from one of the thunderbolt ports (different bus to the RAID 1 and 2). As I have completed editing and just need to export 30-40 1 minute clips I’ve removed it to save bandwidth (and the constant fan humming).
Thanks for trying to help though Bill.
Apple have advised me to take the Mac Pro to my nearest shop and book with a genius to see if a GPU or RAM stick has gone faulty.
Co-owner at Pollen Studio
http://www.pollenstudio.co.uk