thank you for test
it seems that your shader also have same problem
i changed little bit. watch red boxes please.
and rotated plane 180degree.
it looks not bad but can see refraction line
video
I know it’s a very late answer, but if anyone comes along the same problem and reads this:
The refraction input is supposed to be a fixed value, like 1.333 for water. It’s the Index of Refraction (IOR) There are lists online about different Materials, sometimes even with different temperatures.
The Distortion will be automatically calculated by the normal of the surface. It also will be taken into account, if you put a normalmap into the material node.