I have never had a door lock apart to know what is supposed to keep the water out, I never recall my parents having to deal with frozen locks on their 240D, so I may take one apart to see if they can be fixed so I do not have to deal with it any more on my 300D

I decided as long as water can get in, I might as well work with it ,and just inject a small amount of RV antifreeze in the lock to keep the water from freezeing, and it doesn’t freeze up. I would much rather just not have any water in there in the first place though..