The moisture on the underside of the hopper lid is an indicator that some exhaust is finding its way there due to more combustion air coming in than can be exhausted out the flue. If your air setting on the combustion fans is the same as it has always been and you never had the problem before then you should look for fly ash blocking the exhaust. If this is your first time ever using both burners, you may need to cut the combustion air being fed into the burners.
I don't have a 140, but the note below mentioning where other 140 users check their over fire draft came from this thread... Alaska 140 hopper stink?
"If your stove is close in design to my 140 dual feed that is probably the same hole I used to check my over fire settings .
The hole on my stove is located above and to the right of the flue and measuring from the floor it would put it about 6" above the top of the ash door."