It seems that the temporary directories produced when hardcopies are produced are not being deleted in our WW installation. These are the work.[random] directories produced in Hardcopy.pm.
If I've understood the code correctly, those directories (and the files in them) should be deleted as long as
$WeBWorK::ContentGenerator::Hardcopy::PreserveTempFiles = 0
in Constants.pm, which we've checked, and it is.
Any ideas about why this might be?