Hi @koushikwebdesignwork !
This one gave me some trouble, but I found what causes the problem.
It is the animation that you set up on your section .Center.Speciality Cards that affect the positioning of the overlay. The Slide animation make an initial transform on the position of your section and the fixed position is affected.
It is actually quite unintuitive as you would think that a fixed element is only dependent on the viewport…
Removing the animation on the parent yes.
But I think you can still keep a slide in effect on the cards if you remove the div containing the overlay from it.
But then, targeting the good Speciality Pop up when you click on the Learn More button becomes a little more tricky. You would need to add some custom code I believe.