Yes. I had an old KA until a few years back. Every year or so it would start dripping housing/packing oil like you describe...I abused that machine by asking it to mix and knead bread of all things ;o) I used to have it re-packed with grease, but after doing this a number of times I felt I was fighting a losing battle because it was happening more frequently. I finally gave up the ghost and purchase a new stand mixer (Viking). But you should be able to eke out a few more years of life by re-packing it.

I'd say that the grease isn't breaking down. That is VERY unlikely to happen.

I'd say it's actually the shaft seals.

Replacing the shaft seals may be an option for you, or it may have to be done by a KA service center, I really don't know.