I have a simple fluid simulation set up and, I have an "effector" object that is supposed to be making the fluid collide with it. The problem here is, I've set the effector strength "Surface Thickness" to 0.3 which normally is quite enough. But here (as you see encircled in yellow,) the fluid is passing right through it. So I can turn the "Surface Thickness" up a little bit and it works then except, then the FLIP particles ride obviously on top of the plane ([picture 2] which obviously doesn't work.) I've even tried to set the "Sampling Substeps" up a bit but to no avail. Why is my fluid sim doing this?
It appears that you found the solution? Your blend file worked for me. The Collision Effector surface thickness has to be at least 0.5 Thickness, which I have reported as a bug. And I have no idea why the default Sampling Substeps is '0', when I find that is often insufficient.