Hi, We have exactly the same spa and our 2nd foot jet popped out last night. Not happy! I have asked the company hottubsuperstore which we purchased it from (and who give excellent customer service I must add!) to investigate if this is a design flaw and what will happen if it continues to pop out every 6 months when our warranty expires. The plastic ridge that holds it in seems to thin for the amount of pressure that it is expected to withstand. I used to use the jet daily, when it broke I was reluctant to use it, I did notice recently that the jet has been opening on its own a small amount, not sure if that is relevant to it breaking? when I hear, I will let you know what they say.
So you are not alone in this problem, and its good to know we are not alone!