Hi, i need some help with a simple design that has a slicing problem, and I do not know how to fix it.

The solid has been extruded using 2 surfaces ( boolean union ) in to one.

When look at the export STL file, it has a mistake in one curve part that result in a slice that is not in line with the Solid model.

can you help me to correct this? 

I add a picture of the sliced model

thx

peter