Steam build errors

Hi all,

I've got a really painful issues with steam builds since updating to 2018.3.3. If I build with steammanager enabled it crashes the game when installed on steam, testing is a pain too as the pc boots up my steam folder version instead of my offline test version. I usually got around this by just copying my test version to my steam install folder but inexplicably this is no longer working and even after overwriting my files the steam version magically loads (No idea how!).

Any advice on if steambuilds have issues with 2018.3.3 or how to test to find the problem would be massively appreciated. This is my first steam game, everything was fine before updating. Roll back is also hugely painful due to new prefab system which does not allow me to keep my scene in unity 2018.2