Unity 5 - Terrain Detail Density/Distance not sticking?

Hi, so I've tried googling this multiple times but to no avail. My game is going very smoothly, it look's great but im hitting 4-5million verticies at any given time and a lot of my testers are unable to run the game with an average fps above 20fps.

The problem is when I bring down my terrains "Tree & Detail Objects" sliders (Distance, Density) it works fine and my game is running at about 1-2 million verticies without any visual downside. This is awesome and a great workaround to keeping my dense forest (I have very dense fog anyway, render distance is not too important to me) however when I come back out of testing all the sliders are completely maxed out again. Am I doing something wrong?

I've checked all my scripts (I'm 90% sure) and could not find anything that would effect the sliders (not really sure what to look for in the first place tbh).

Any suggestions would be super as my game is currently at a standstill.