poudriere cluster error: contention?

[Anton Shterenlikht]

I'm building science/paraview in poudriere with -J 4.
paraview pulls in quite a few ports, many of which
are included in KDE/qt-everywhere-opensource-src-4.8.4.tar.gz.

In my case devel/qmake4 build fails with:

pax: File /usr/ports/distfiles/KDE/qt-everywhere-opensource-src-4.8.4.tar.gz
 was modified during copy to /pdr/data/build/ia64-default/ref/../01/portdistfiles/KDE/qt-everywhere-opensource-src-4.8.4.tar.gz

The full log:

http://eis.bris.ac.uk/~mexas/poudriere/bulk/ia64-default/2013-10-08_14h41m14s/logs/errors/qt4-qmake-4.8.4_1.log

Is it possible that several builders
compete for access to KDE/qt-everywhere-opensource-src-4.8.4.tar.gz ?
Is it possible that this would lead
to the above error?

Thanks

Anton