I've had a lot of problems with this product.
The first one had an issue where it would not lock into position. So I took it back to the shop. They tried as well and in the end they replaced it.
The second one buckled at the arm which locks down. At first I thought it was my wife using too much force when locking into position but later found that my friend who has the same product had exactly the same problem.
This product has a design flaw. I couldn't be bothered going back to the shop and getting a new one.