Things possibly being "allowed" in the past doesn't change the fact that it was possible at this time. Nor does open doors INSIDE a claim make it possible for outsiders to do anything or even getting inside without placing a wasteclaim. This argument is invalid because it could be used against 'other bugs' that happened.
As far as i know, the previous scents were there because one of them teamed up with Darwoth, and thus allowing him access to that base. That person was removed from said claim, so nothing could happen now.
I'll stop discussing this matter though, I don't wanna keep you off your more important work, you're the judge here, you know (hopefully) exactly what happens and you have the power to do anything about it.