Hi,
Have you tried the settings from the driver?
Just got a D125 with the built-in controller installed last week and it's already started an argument with mPDF. The way we have that configured it only wants to output A4-size PDFs. I went into the print settings on the D125 and set "Substitute Tray" to "Use Closest Size" and "Paper Type Mismatch" to "Print" but it's still holding the jobs.I expect I'm missing something simple here, that's been the story setting this printer up so far.