Question GPU Usage - "Other" - Performance bottle neck

I am working on increasing the performance of my game. right now it runs pretty well on modern hardware but i am wanting to see if i can squeeze out any extra frames to help people with weaker machines.

I am believing that my GPU is my bottleneck as most of the rendering from the CPU is waiting for the GPU to catch up. When I turn on the GPU Usage in the profiler, about half of it's performance is being eaten up by "Other"

I've got no idea how to find out what this Other could be referring to.

These are the stats when I am running it in low quality mode, so everything is turned down. Other still takes up about half, sometimes a bit more than half, even when I am playing it at a higher quality setting


My game has large maps that are about 1 square mile, it's a flying game, so lots of trees and open spaces.

I have a few baked reflection probes in my scene, would that be what is causing the 12.1% hit? are reflection probes that expensive?
Any idea what RenderDeferred.ReflectionToEmissive is referring to?