The left stop lights on my Big Horn 2010, 3055 were not working, however all the other lights on the trailer functioned OK. All lights also worked OK on my tow vehicle a 2003 GMC 2500 HD Duramax. After reading about a similar problem that was discussed on The Diesel Place forum I took my tow vehicle in to my GMC dealer. It was determined that the hazard module was faulty. The module was replaced and the left stop lights and all the other lights now function properly. Apparently the stop light function for the trailer is routed through the hazard flasher module. Hope this helps someone else since it took me quite a bit of time and research to solve this problem. It was also a little more puzzling because when I would first hookup and check the lights everthing worked, however after a couple stop light and turn signal cycles the brake lights on the left side no longer functioned, I was lucky since I still had right side stop lights. I understand sometimes both sides fail and there are no trailer stop lights at all.