Update. I was not imagining things , the DAC can not cope with more than one active SPDIF input. It has trouble switching between any Redbook and HiRez source across it’s SPDIF bus. Turn one unit off on Coax 1 and the unit on Coax 2 will resume play. It is the input board’s logic or it is not well insulated.
It isn’t broken in the traditional sense , but it is not working properly. No problem if USB from Aurender to DAC and Optical from Bluesound to DAC .
Unfortunately it is a recent build and has the most recent firmware so at this point as really believe it is a hardware limitation.