Had the same problem. Went to the hardware store and bought the smallest rubber washers/ O ring they had, one for each vent. Took the loovers off and then placed a rubber washer/O ring over the loover pin and re installed. Never again have I had a problem. I can close them, open them, gate them part way. No problem. There was a thread on this subject about a year ago.
http://www.forestriverforums.com/for...open-7368.html . There were several solutions listed. Good luck.