This is a "cost effective" thought process ... Soundsmith offer replacement cartridges for the B&O design. It may be cheaper and more effective to replace, rather than repair? That will require research.
BTW -- the MMC5 is compatible with the others in the series (MMC1, 2, 3, and 4). So there's no harm in getting a lower number. In fact, it'll be an improvement on what you had before.
I know about soundsmith and the cheapest replacement they have is about 200 dollars it would be an MMC4 the MMC 5 is the entry level cart and for some reason they won't rebuild them.Thanks for the suggestion though.
Bennie at Amina Audio did my mmc5 last year. It came back as an mmc4! Took 3 weeks, cost was $125 + $15 for shipping. Sounds great. Easy guy to work with.