Cheap construction. The frame lacks rigidity and/or the subfloor is not well-attached to it. Often both of those. The more the frame underneath twists and shifts during travel or leveling, the more the subfloor moves. As others have said, sometimes screwing the subfloor down works for awhile, but the movement can loosen it up again.
Twilight advertises their great construction
and high quality, so file a warranty claim. Maybe they will actually do something about it, but don't be surprised if you get the run-around from dealer or factory.