Black borders Displace - Arnold Issue


Hello there,
I am quite new to surfacing and to Arnold.
I have an issue with my displacement map, when rendering, I am getting darker borders on the displace, as shown on the pictures below:

The higher I set the displace scale, the darker are the borders.
I have a simple Arnold Skydome light.
I am using simple jpg maps (that have been converted to .tx files by Arnold)
Do you know how to fix this?