Wow. Your experience with your Momentum is much different than ours. We just celebrated our 1 year anniversary full-timing in our 380TH and have travelled 11,000 miles. We've had a few issues, but Grand Design responded and took care of every one. Our rig spent 1 day at a dealer and every other issue has been parts replaced by me that they shipped at their expense to wherever we were at the time.
As for the Owners forum, I've been a member over a year and it is operated privately by an individual owner ourside of the company. I'm not sure why you thought anything was tightly controlled as I've seen plenty of rants from people with problems. However, in most cases when they went to the company the oeonl was resolved. Anyway, sorry you've had a bad experience and maybe tol hAve better luck with another company's product. We plan to be using ours for years to come.
