Boolean Modifier (Difference) Issue Persists Even After Applying All Transformations, Recalcing Normals, and Fixing Non-Manifolds I've been wrestling with this issue for the past couple of hours. Here's the gist of it (version 2.8):

I'm trying to "shave off" a piece of my mesh, and have a designated "knife" object. I intend on using the boolean modifier for this. Before using the modifier, I made sure both objects were water tight with correctly facing normals. I also applied all transformations. Yet, I still have an issue. 

After applying the modifier, the "knife" object only "traces out" the pieces of the mesh that I wanted to cut, and does not actually delete the intended vertices. 

I've included a YouTube link to a 1-min video that describes what I'm talking about (https://bit.ly/337UaC6). 

Here's also a link to the actual blender file: 

I've also included some pictures of my "main" object:




Please let me know if I need to provide anything else. Any help is appreciated.
There are were inverted normals, so Shift+N to recalculate them. 
Overlapping edges between boolean cutter and source object. This is healed by moving edge away from the cut. It's a front view: yellow edge is source, white is cutter:


Lots of ngons, so consider doing retopology. I added Triangulate modifier to make it more boolean-friendly:




Also keep boolean object's geometry as simple as posible, avoid excessive edges which doesn't contribute to final shape.