I am a new owner of an outdoor umbrella. I bought it used, and noticed that it moves a little when the wind blows. The manufacturer says that this is normal, but I have not been able to find any information on what causes it to move.
It's called "jointing" and there is a good chance that it will continue to move. It will eventually wear out over time and then you'll need to replace it. It's a little bit like a car, you don't expect a new car to go "wobbly" in the first few months.