Tapered Extrusion Surface + Plane Sculpt not working

Hello,

Why does the Sculpt command display "try with different inputs" error when attempting to create a sculpted feature from extruded surface (with taper) and a 3-point plane? This seems very straightforward and I can't understand what it doesn't like (the most frustrating part of course is total lack of explanation in the error message).

Zipped part and illustration of desired cut are attached:

TopDiamondSurface: the tapered surface extrusion.

TopDiamondFirstSideHalfway: provides a third point for 3-point plane defining the first slope cut of the TopDiamondSurface (slope "end"). The first two points are placed at both sides of the slope "start".

TopDiamondFirstSlopePlane: the 3-point plane that defines the first slope cut defining the top of TopDiamondSurface.

TopDiamondSecondSideHalfway/SecondSlopePlane: same as above, but for the second slope cut defining the top of TopDiamondSurface.

Sculpt is not included because the command fails. For Sculpt command, select TopDiamondSurface, TopDiamondFirstSlopePlane and TopDiamondSecondSlopePlane as inputs.

After opening the file, right-click last feature in the list and select Move EOP Marker from shortcut menu to make all features visible.

Hopefully that makes sense! Thanks for your help.

SculptNotWorking.zip

see attached

SamplePart_JD_Rev1.ipt

SamplePart_Illustration.ipt

Thanks! I didn't realize the surface extrusion simply didn't reach the roof created by both planes in one area.