Hi mike
I think I have worked it out mate. I will try some more bulk printing to make sure its consistant. I have set spool with delay of 3 seconds fast printing.  Seems ok.  hopefully.  It seems to allow print distributor to do its job of load sharing. BTW i have modern dnp printers and a i7 quad laptop with 40gb of ram and 1070 8gb videocard.  the biggest jobs and movie editing in 4 k barely slows it down .  I can print 300 6x4 prints from kiosk and no worries at all mate.  I do think there is a blocked pipe somewhere that does not allow qimage to communicate with print distributor properly.. All i can do is apply logic to what I know is fact.  I'm not a techy just a thinking bushy.  I have been in the industry for 20 plus years printing and everything photographic.
regards
wayne