Think of your stirrups as snugly slippers, soft and warm and gently supporting your foot.
Then, forget about them!
Instead of driving your heel down and pressing on your stirrup, which will cause you to push off the stirrup when rising, (took me ages to stop putting too much weight in my stirrups!) try to imagine tightening the cords in back of your knee and/or achilles to RAISE YOUR TOE.
Try not to tip your ankle, keep it level, always with the toe forward. Think of your ankles as the soft and flexible antenna.
The stirrup has absolutely no use whatsoever other than somewhere to softly rest your foot!
As always, enjoy