No mods needs. You just need to clean your smoker occassionally.
Just clean the hole occassionally. The problem is gunk is getting in the hole, and usually during cold weather cooks, the condensation builds up and drops back down.
The easiest thing is to find a pipe cleaning tool (plumbers section) and it's made to clean out pipes. But a good rag will do fine.
It doesn't happen to everyone, seems to be certain temps and it's very localized.
eyebuster. Nice looking attachment, but I don't think it's needed for everyone. With your set-up you're having a lot of condensation (because of the vent and enclosed space) so that's the cause. If it works for you, that's great, but the solution is just a cleaning one.