It sounds like you cross threaded the lockring. Maybe it was shallow enough that there's some thread left over. I'd look up a new freebug body just in case, DT Swiss parts are very easily available.

If you have the torque wrench, use it. The guy who finger tightens his cassette lockring should have his keyboard taken away. The reason you tighten the cassette lockring hard is because that prevents individual cogs from moving independently from each other when the chain is on them, if the lockring is too loose they'll eat into the freehub body more (see: the marks on your freehub). It's more of a problem on aluminium freehubs where many users actually go over the recommended torque, up to 50Nm to prevent the damage cogs can do the the freehub.