Report of poor gaming results with AMD Ryzen 7800X3D and ASUS RTX 3070
That's what I initially looked at.
You got there early! I'd make sure they're positioned correctly first. If that works out, I'd definitely go for separate cables like you suggested.
Understood. Attempt the individual parts and hope for the best.
Also, if your friend is a really good friend, perhaps they would let you try their card in your system. That's a great way to rule out a failing gpu.