I am getting the same issue as well - my phone SHUTS DOWN when charging on a Quick charger. Regarding it shutting down at 42 degrees - I have placed my phone on my vehicle air conditioner and it still shuts down when using Quick charger.
As I am using a tencent edition ROG 2 - the ASUS service operator in my region does not accepts the phone - even for repairs.
As of the slow charging method - it works for me. For those who could not send your phone to a service center - USE A SLOW CHARGER. Or a USB-A cable paired with USB-C adapter. This combination works and it does not shuts down the phone.
I am not saying it is a software issue. I am saying I found a hack that works. Hope to share it with others.
Hope you understand.