Meltdown success stories?

Coach Davies, I tried overhead squats for the first time today, and was shocked only to get three reps with 75 lbs. I’m 6-3, 195, 31 years old, former collegiate high jumper (6-6), currently snatch 165 lbs, front squat 200, full back squat 235. I’m wondering why the heck I’m so weak in the OH squat. I was able to Overhead lunge with 100lbs, which is a little better, but not a whole lot… Thanks for any advice, Pete