An interesting problem that I cam across a few weeks back on the Brother HL5450DN laser printer.
The Brother HL-5450DN was producing a shadow / smudge after all print.
With some testing and a couple of different drum / toner combos and a bit of research.
It turns out this series of printer has a issue with the fuser that causes the fuser to slip and smudge the printing.
Since this one I have also had a printer slipping so bad that jamming was starting to occur.
To date I have not found a fix for this fault aside from replacing the fuser – Hopefully that can be done under warranty as they are quite expensive.
This problem almost certainly affects all the models in this series: HL5440D, HL5470DW, DCP8155DN, MFC8510DN, MFC8910DW, HL6180DW and MFC8950DW
The printers I have seen with the fault have normally done about 80 or 90 thousand pages.
