Why does deployed ios app crash on a shader that compiles fine in Unity?

The answer, I want to share with the world -

Unity does not catch this error, and it works fine in the editor, even when compiling to gles. You cannot dot product different float types.

 half3 vectorOne
 float3 vectorTwo
 
 half result = dot(vectorOne, vectorTwo)

Instead, change both vectors to the same type (float3 or half3)