Iray Base Bump Issue

Hi all,

I'm trying to raise the base bump value to more than 1.0, but sometimes that gives me lines or "edges" or "borders" on my figures. Sometimes it does, sometimes it doesn't...

I've attached two pics. Both textures have the base bump raised to 5.0. One of them (basebumpok) is fine, the other one (basebumplines) gives the issues I'm tlaking about. They don't go away unless base bump is set back to 1.0 again, but that takes a way frothe glossy effect I want to achieve...

Does anybody know how to resolve this?

Thanks a lot,

Me