Really high rendering time in build.

I’m trying to develop a game for the Daydream platform and I’ve come across a really wierd issue that will not go away, no matter what I try!

I’m using Unity 2017.3.1f1 at the moment, Occlusion culling on, shadows disabled, single pass rendering, textures batched and atlased, static flags set, 1 skinned mesh renderer on scene at this point, Vsync off, AA off, 16 bit buffer, depth and stencil off, 24 bit buffer enabled for daydream as without it meshes look horrific! Vert count is below 200k, Highest setpass calls are about 25. There are no transparent objets in the scene, nor
Basically every single optimisation trick I can try to boost FPS, I’m doing. I only have a couple of scripts using Update, and only one using FixedUpdate for physics.

In the editor, everything looks great on the profiler, no trouble here!

When I build however, my rendering time shoots up! The strange thing though is the only objects I find referenced are sprites, that aren’t even part of the game, screen below for reference.

What could I possibly be missing here? Really appreciate any help!

Image below is the scene in question, nothing too complex