Panasonic dot matrix leaves ink smears on pages

I've got an old Panasonic KX-P1123 24 pin dot matrix printer that used
to work satisfactorily.

I kept it stored in a locker for a couple of years while I grappled
with a bout of homelessness. Now that I'm newly ensconced in a tiny
public housing apartment, I dug out the printer and bought a new
(generic) ribbon for it (I failed to keep the packaging, and the
ribbon case has no identifying markings on it).

Since starting to use the printer again I've encountered two annoying
problems:

1....

Panasonic dot matrix leaves ink smears on pages