[pdftex] Sophiscticated error

[Aleks Kleyn]

I create two pdf files using pdflatex. When I compile B.pdf I use
\externaldocument to get references from A.aux. Somewhere in the file A.tex
there is error, however I see the problem only when I compile B.tex. Is here
the way to get extra output so I will be able to find problem.

I cannot create min example because I do not have any idea what I should
extract.