My title is awful, but got this thing from Amazon and it seems to be helping. My left/lead elbow was always breaking down on backswing leading to bent left elbow (aka chicken wing) all thru out my swing. This device will click when elbow bends a bit.
https://www.amazon.com/gp/product/B000FFYIQM?ref=ppx_pt2_dt_b_prod_image
https://www.amazon.com/gp/product/B000FFYIQM?ref=ppx_pt2_dt_b_prod_image