It's amusing to read these reports.
I have about 24 Zuiko lenses, all but 3 were purchased used. Remeber that most of these lenses are 30 ro 40 years old.
About 1/3 of my Zuikos have some kind of internal haze or dust in them. The need a good cleaning and lube. It isn't that they don't all work fine but obviously some are sharper and more contrasty than others.
Out there in the world are many homeless Zuikos that haven't had a bath and a shave for a long time.