It’s because you have scroll animations directly applied to your button(s) and some properties interfere with each other.
You could kind of fix/override things with relative styling, but there is too much involved, like transition duration, transition delay, transition property, etc. It wouldn’t make any sense.
Using animate on scroll, I’d suggest to add an additional container to your individual elements and apply the scroll animation to it instead of the actual element, to ensure they act as intended.
This is my general recommendation when using scroll animations. Always add a dedicated animation wrapper.