Strange print issue

[joehayes999]

This is a sample print from a Brother MFC L-2710DW. As you can see some characters are skipped only to be printed quarter of a page later. This occurs on both print and copy, so it is not the driver. I switched the drum and toner with another machine and the problem didn't move, so the problem is not these.
It is like it is printed on to something and then printed off it again then the drum rolls around. It occurs in the same place each page.
Any ideas?

 

[k_mohr3]

Seeing as you have already done a swap on the drum unit/toner, I would see if I could see into the fusing unit through the back access door. The fuser should be visible from the back - check both rollers in there for damage. You may also be able to see it from inside the machine with the toner / drum out of the way.