Most clip-on systems have a certain amount of float where they won't unclip. There's also a tension adjustment which adjusts the release force needed.

The key to releasing is to use a quick snapping motion rotating in or outward to release. It might be you're having problems beacuse you wait too long to release then lack confidence so you panic and try to pull up as you release which stiffens the action.

Start by checking your pedals, clip in your shoes (off the bike), then give them a sharp push sideways to check that they release nicely. You might also back off some of the tension. Then sit on the bike next a wall, and practice the release motion a few times until you're comfortable, before riding. Then prevent the release crisis by releasing well in advance of stopping and leaving your foot on but not in the pedal. Release with the foot near the bottom of the pedal stroke where you have the most freedom of rotation. Get used to doing this with one foot all the time, so you have the control of having the other engaged if need be. (this can lead to a comical slow fall if you're standing with your weight shifted to the wrong side). Once you have your release technique down do it the same way every time, so it's a reflex and you'll do it automatically in an emergency.

Within a day or so, the comedy show will be over permanently.

BTW- some people, including myself have much more success releasing turning the heel in to the wheel rather than out. My right road shoe has a good size scuff area by the heel from contact with the tire so, I glue a piece of leather there and replace it from time to time, but I find inside release to be easier on my ankles and knees, so continue to release this way.