Hi.
I noticed this 3 or 5 years ago and currently it seems that is not solved by Autodesk team.
Calculated material is from 2 surface sections (above yellow surface section and below orange surface section)
As you can see, this material style has a pattern associated in its shape style with ANSI31 pattern in light orange.
However if the section view has another surface sections and they are inside or partially inside of the result area, pattern also includes their lines:
Look at if we put this material to the background, surface sections are on:
So if Sample Lines have another Surface sections (even if they don´t participate to calculate this material), then hatch is wrong. If hatch is SOLID you can also see this lines if you select the material.
This is very annoying specially when we convert to ACAD dwg and hatch boundaries are not correct.
