are you turning your shoulders or your hips?
i find that if i only turn my hips i land 90 all day.
if im going to do a 180, or any spin, i first wind up my shoulders as far as i can into my spin
direction, then turn my head the same way as i pop. as the motion
becomes more fluid it becomes harder (for me) to 180 than to go 3.
also i learned flat instead of putting in an ollie. i wound up and just spun
180 riding flat, letting my shoulders wind up for the spin and my hips to execute.