It isn't known. Might just be with very large files though, or a specific bug in a specific firmware.
Test the size thing with the attached pdf
Latest firmware is here
Im testing a workflow for an end user. Due to size of files when printing across the network, it may be best to submit job(PDF file) directly to a 7855 via Centreware. The PDF has some pages in landscape, some in portrait. When we request duplex, the 7855 doesnt duplex it. Is this a known issue with mixed orientation PDFs?