Ok, so in this case your 850W PSU *can't* push 850W, because this isn't actually an 850W PSU. The manufacturer is lying, basically.
Your PSU has a single 12V 70A rail which is only 840W, and you should keep the load on that circuit <= 80% for safety (note that this is not the same as efficiency as described above, this is about the size of the circuit itself), so you can realistically only draw 672A from your PSU. Your GPU is drawing 550-575W, leaving only 97-122W available for the rest of the system.
It's highly likely the crash you are experiencing is due to system instability caused by rapid voltage drops on other components (CPU, RAM, etc.) Get a real PSU and see if that doesn't fix your issue.
Your PSU has a single 12V 70A rail which is only 840W, and you should keep the load on that circuit <= 80% for safety (note that this is not the same as efficiency as described above, this is about the size of the circuit itself), so you can realistically only draw 672A from your PSU. Your GPU is drawing 550-575W, leaving only 97-122W available for the rest of the system.
It's highly likely the crash you are experiencing is due to system instability caused by rapid voltage drops on other components (CPU, RAM, etc.) Get a real PSU and see if that doesn't fix your issue.