Best robot hoover for thick carpets??

[Howandwhy]

I have very thick carpets and am struggling to find a robot hoover that can manage them.

Does anyone have any recommendations please? X

I have the original roomba, it's probably the lower end of the range now. It does a great job on my thick carpets BUT it's made permanent tracks around the walls. I think it's the way they pivot to stay on the wall, nothing I do has improved it.

Thanks for responding. It's a pitty about the marks on the wall.