Hi,
Since some time ago I have had this issue and I tested a lot of things to solve it, but I never found a solution to it, and I thought that maybe I should post it here.
Currently I am creating a river shader that works with a spline, my idea is to make a mask that detects that is the next part of the spline is a slope, so I can use that information to make the panning of the texture quicker (to simulate water physics), but when I do this the UV values goes nuts or makes weird seams.
The only solution I found is to floor the values, but that makes the tiling very noticeable, so isn’t the ideal solution.
For reference I will upload photos of the shader and my code.
*Also, for the project’s needs, I need to use a Shader that I already made, so I am not interested in using the ones that Unreal has built-in.