It transpires that it is /not/ the PDF/X-1A \specials that are the root cause of the problem. It is the use of
\input eplain
\beginpackages
\usepackage {color}
\endpackages
If I replace this with what I believe to be the functionally equivalent :
\input miniltx
\input color
all works as in 2014 !
** Phil.
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