Obs and / or Fortnite and / or PC crashes?

I have a Ryzen 7 2700x processor, a B450 M motherboard, 16GB 3000MHz RAM and a RX Vega 56 installed in my PC. If I want to stream either my game crashes, my OBS or my complete PC crashes. I play Fortnite on Low Settings 1080p Full HD Settings on 144FPS and stream with 720p 30FPS. I do streaming over the graphics card. So the settings would even have to create a GTX 1050ti. Can someone explain to me what it could be. My processor will only warm up to a maximum of 60 degrees.

Power supply too weak?

Have a 550W power supply from Bequiet. That would normally be enough

Yes that's enough thick. Look if all the cables are really tight, maybe one has relaxed and updated all drivers.

Maybe the power supply is just broken

Drivers up to date?

What is the temperature of the graphics card?

Where do I see that?

Yes

In HardwareInfo64 or MSI Afterburner, both installation tools