Being a new unit, I would have them hand packed and the brakes properly adjusted. I always repack mine yearly, also a good idea to adjust your brakes annually also.
In the past I have found broken return springs, broken adjusting wheel parts and even lining that came apart from the shoe. All had been good the previous year, averaged about 5000 miles a year.
03 Silverado cclb 3500 drw, D/A, Reese 22k hitch
07 Alfa SeeYa Gold 30RL,2 slides,power everything