Printer, works but not perfect (South Heighton BN9)

This is a Brother HL-3170CDW printer, about 8 years old.
It's done us well, but has started leaking toner (see blue blobs on the photo). I've tried cleaning (hoover & isopropyl alcohol) & have replaced the transfer belt, but haven't been able to get rid of the blue blobs.
I've spent enough time time & money trying to clean it up, but might it be useful to you?
Collection from Denton Village, Newhaven.