Map Voronoi to adjustable curved surface

I've created a 2d voronoi with an offset and mapped it to a curved surface, I then projected the map so it fit the surface exactly. The curved surface is part of an adjustable tablet dock I'm creating so its size/shape changes when I adjust some sliders. All went well initially but as I began to adjust the surface the mapped pattern started doing funky things - as pictured. 

Can anyone help me out with this one?

I intended to map the same Voronoi pattern to a surface directly behind the one I'm working on and then loft between them to create a curved solid sheet with Voronoi-patterned holes through it. If there is a better way to do this please advise.

I'm brand spanking new to grasshopper so please forgive me if this is a stoopid problem. Have scoured the forum but can't figure out whats going wrong.

Thanks!