This is not outline.
This looks like the Scorpion mesh wireframe, edge for edge.
Neither the outline shader, nor the previous stencil outline thingy, is supposed to do this or afaict even be capable of producing this.
There is, however, a console command that's supposed to do just this (but afaik it also suppresses normal drawing of units) :
/WireModel (unsynced): Toggle wireframe-mode drawing of model geometry
See if invoking /wiremodel or /wiremodel 0 ingame interacts with your problem.