Since the rendering subsystem change didn't work, I recommend checking for duplicate particles in your particles folder. Locate your FeralHeart folder on your PC and navigate to FeralHeart>media>particles. In that folder you will need to look for any duplicated particle files. Duplicated particle files will usually have the same name as another particle file in the folder and will have a "_0" or a "_1" within the file name. If there are any files like that in there, delete them and try to start up your game once again.
Another recommendation I have is to Run your game as an administrator. You can do this by right clicking your desktop shortcut and selecting "Run as Administrator" if the option is available.