Re: pdflatex failures on big-endian architectures (s390x / ppc64)

    Maybe for any reason still the 
    old (unfixed) pdftex binary is called..

pdflatex is a symlink to pdftex, ordinarily in the same directory.
Did you update pdftex in the place that pdflatex points to?

You could equivalently run
  ./pdftex -fmt=pdflatex testfile.tex
if pdflatex.fmt is somewhere known to TeX. Or could give a full path to
-fmt. I think.

Just grasping at straws ... -k