When holding sneaking key too short it makes screen bouncy

If I press my custom "ctrl" (when its default it glitches too) key for sneaking my screen bounces, but only if i press it for too short, if i press it for longer then its normal. But still like 80% of my sneaking is short pressing, and it's really annoying when you are trying to speedbridge. And yes i didnt press the sneak button twice, it really looks like being pressed two times in a row but its not, please fix