Rigidbody sphere slows down but keep rolling

I'm dropping four spheres down a ramp to test their drags. I did an experiment in this video, as you can see each spheres and their properties, they all slow down to about 3.5 and then keep rolling. I'm not talking about the speed changing when it looks like they stopped, that's not the issue. Their speeds, after leaving the ramp, looks like something like this graph: And this change of speed happens to every sphere, some of them slow downs to a halt faster, but the weird change in speed is still happening. Each ball have a different drag setting, but all of them share the same physics material (0.1 on static and dynamic friction with multiply) as the floor they are rolling have also a physics material (0.8 on both frictions also with multiply). I'm using Unity 2020.1.14f1, gravity on Y is -100. I can't recall if I did change any other settings, if you need more info just ask.