I really can't comprehend why people have trouble scoring subs.
Easiest thing to do ever. The system is so broken. Unless you are completely inept at spinning and don't make full circles, it's such a ridiculous system. Just make sure you are doing a level 3 sub and not a level 1.
My entire playthrough on Expert career mode consisted of grabbing double underhooks, pulling guard, mission control, level 3 triangle choke. 1st round sub of the night every single time.