Unlit ZTest Always incorrect edges order

Hello. I need to show arrow object on the top of the others. So I created new default Unlit shader and put there the “ZTest Always” setting. Now the object is rendered on the top of the others but I have the problem. For some reason some of the object edges are rendered in incorrect order.

Object from different views

3D modeler who made this model said that all normals are okay, but it seems strange to me that only 3 out of 4 these “corner” edges are showed incorrect.
Could someone explain what’s the problem here please?