I think I may have caught the little buggar!!!

My son works for one of the leading airline carriers. They regularly check there aircraft for leaks. The jest of the story is that since you can not smoke on any carriers now, finding these leaks is harder. Prior, all he had to do was look for the smoke stain's on the aircraft fuselage, as the aircraft is always pressurized in flight.
If you pressurize your RV, you will be surprised as to all of those air leaks you will find.