I’m having several crashes of 123D Design when I:

Merge

Delete

Extrude

Tweak

Move

Pretty much all the functions. Could this be caused by too many sketches in the work area? If so how can I delete sketches?

Thank you all in advanced.

123D crashes all the time when performing operations on complex meshes. It may be that the meshes themselves are faulty and need to put through MeshMixer or NetFabb to repair them.