Could you send me the model for investigation? Are you sure the distance is not set to too high? How does a value of 0.01 look?
Yes. Here is the original surface without thickness:
no thickness.3dm (215.8 KB)
Here is the same surface with moderate (0.8) thickness:
thickness bug.3dm (199.8 KB)
No. diameter of the original surface is about 5 units. One spike begins to grow at the thickness distance of 0.7. The following screenshot illustrates the spike at thickness distance of 0.8.
I see the bug! Reported https://mcneel.myjetbrains.com/youtrack/issue/RH-43765.
I can’t reproduce this bug anymore. In addition, at 0.8 this is already starting to be too much for a mesh “trick” - you should really offset the brep.