Probably standing on your toes and pushing the heel down instead of letting the weight sink into the heel all the way down from your glutes to hamstrings then the calf and Achilles’ tendon. It’s not about how low the heel is, its where the weight is and often the really low heel looks great but is not properly carrying the weight. Judges sometimes reward the position without realizing it’s exaggerated and not properly carrying the weight, until they lose an iron anyway or get jumped loose.
Took me a very long time to get that, my regular trainers didn’t really realize it (trainers keep learning too, new thoughts and / or how to better present them to clients). Took a popular clinician to point it out to me and my trainer that the problem wasn’t not being able to get the heel down, it was not much weight was making it to the heels. He described it as getting lost on the way down to grippy thighs and pinched knee. The heel has to carry the weight to stabilize the leg which anchors the foot in the iron.
Hope that makes sense, it was a huge breakthrough for me and the feeling when you get it right is amazing…but you get sore all the way down the back of your leg, almost from the waist down when you start getting it. Increasing core strength really helps you master being able to align your body to allow that weight to get where it belongs.
I wasted a lot of time trying to push the heel down without understanding the lower heel meant nothing if the weight was stopping in the ball if my foot, more mimicking correct position without really creating it. Blamed inflexible ankle, injury, etc. instead of the real root problem. Makes a huge difference in how strong and secure you feel thru your legs when you “get it”.
Try taking a proper position then standing in the irons dropping the heel as far as you can then sit down without moving your lower leg forward. Do not let shoulder fall forward either. It’s a feel thing more then anything else, feel it down the back of your leg, in your calf not your ankle. Then do it at the walk, sounds silly easy…it’s not.
BTW, proper position in the saddle is a line from ear to shoulder to hip to heel. Hold that, you’ll better control where the weight goes…sometimes learn your saddle isnt doing you any favors as well.