Front Squats...
I think I got it figured out... The problem I realized is... since the exercise is new to me and I had that subconscious fear of the bar rolling down, I was gripping the bar with the tips of my fingers to secure it... but what I was doing is actually pulling it out of place. Once I realized this I tried to just lay my fingers across the top of the bar, and there u go... BAR DIDNT MOVE! and if it did, it was only slightly. So I think other beginners may be doing the same thing... which is why "you have to get used to it"... subconsciously once u get comfortable and confident, your won't grip the bar with your fingers because your not afraid of it rolling down... and that let's it stay in place... Also I realized that when I don't grab the bar with the tips of my fingers, I don't have to keep my elbows all the way up because the bar sits in that groove. Before if my elbows drop while I'm gripping the bar with my finger tips, I was pulling it out of place! I thought this may help others...Another thing I noticed is if u notice the bar moves on one side more than the other, when u cross your arms, place that arm on top of the other. i also tried using plates under my heels like people suggested, and it felt like i could go lower while keeping my back straight. Bottom line: lay fingers across the top of the bar but don't grip the bar. The bar will sit in the groove across collar bone, even if elbows come down a bit it won't roll down. Hope what I figured out and posted here will help others with the same issues