How are you streaming? Encoding on the CPU or...?
What are your CPU and GPU temps under streaming load, especially when it crashes?
If you download and run Timespy from 3Dmark (it's part of the 'demo
'), what happens? Does your system complete the benchmark? Can you link to your result online?
If it allows you to run the stress test version of Timespy in the Free version, does your system complete that?
How old is that PSU / how long have you had it?
How long have you had the system, and has it been working otherwise or any other issues? What else have you been doing with it that has been working well?