If you can post your output log (player.log on Mac and Linux), then we can take a look and hopefully see what's happening and what's causing it. This guide explains where to find the log and suggests some sites to upload it to, since we can't attach files here on Steam.
https://steamcommunity.com/sharedfiles/filedetails/?id=463645931&searchtext=log
https://steamcommunity.com/sharedfiles/filedetails/?id=463645931&searchtext=log