extrude thickness distortion

#1

When i use extrude thickness, i get some distortion in the mesh, does anyone know
what causing this?

extrude thickness distortion

#2

or is there any other ways to add thickness to a mesh?

#3

Can you post an image of the mesh before the operation ?

#4

thanks but i found a (hard) way. I think its just a tool not working well on all
meshes, maybe. Something with normals…