How can i fix inconsistency

I set a pb of 16.86 a couple days ago and got a couple sub 20 solves in the past few days but there are some days where i can barely get a sub 30 solve and sometimes ao12 a sub 35 i find this really frustrating as i think my f2l may be the problem and i don't know how to fix it my current ao100 is 28.94 but i struggle to consider myself sub 30