Ever get propane on your hands?..It's tough to get rid of the smell even washing them..When I get a new to me RV,one of the first things I do is the soapy water on connections...There is also a pressure Guage that goes in the line to detect leaks..
Just guessing,if something was getting leaked on for quite a while it would have a propane smell for some time....Air out your TC really good and get someone with a fresh nose to hunt down the area that smells...