Which part of a laser printer causes this kind of blurry print and how to fix it? (Brother MFC-8950DW)

My Brother MFC-8950DW printer prints blurry , as visible on the left of image attached below. The corona wire was cleaned, as well as the drum. After a paper jam occurred and I removed the sheet from the front of the machine, I noticed that the impression is sharp when the toner is not (yet) attached to the page , as visible on the right of the attached image . (The visible dirt is because the sheet has been balled up.) Hence, I assume the blurry print comes from the fuser unit itself. My question is which part of the printer causes the blurry print , and more specifically —assuming it is the

Question by OuzoPower on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.