LG DLG5988 Gas Dryer

I purchased the washer dryer combo 30 days ago. The first thing I noticed was a very hard bang,bang bang when it starts up. The noise goes away after about 10 min. The automatic drying does not get the load dry on the first time. I always have to run it again. I talked to the sales person and he suggested that I replace all the vent pipes. That is a problem because most of it is behind walls. He then went on to stated that he also ownes this model and he has to often set his on manuel at times to get large loads dry. Poor sensor design in my opinon.