"Delete Surface" tool undeletes immediately after doing anything. Plz Help

[AlanRelkin]

I'm trying to reduce the planks on this fence (one way or another), and since I'm using HomeDesignerPro, my options are limited. I thought I was on the right track with the "Delete Surface" tool, but if I copy paste, or even if I try to add this new half-fence to library, it copies and saves it as the original, taller, fence. 

 

Any ideas, kind of hair pulling? Much obliged.

 

Here is a video of what happens. 

[Rookie65]

Maybe try adjusting the height on the last section and add it to the run, and not include it?

[y-g-m-n]

cannot delete pickets from fence panels