What I've learned from this whole fiasco after owning a problem-free 4090 for over 2 years:

1. Don't use 3rd party connectors, and don't use the squid adapter in the box. Use the 12VHPR cable that came with your PSU or GPU. If your PSU doesn't have a 12VHPR connection, get one that does.
2. Don't bend the cable near the connection. Make sure your case is actually big enough to avoid bending.
3. Make sure it's actually plugged in all the way. If you didn't hear a click, it's not plugged in all the way.
4. Don't keep disconnecting the cable to check for burns. The connection is weak and designed to fail after only a handful of disconnect/reconnects. If you followed the 3 steps above perfectly, you have nothing to worry about.

That said, I'm skipping this GPU generation (and most likely the next one as well). Hopefully in 2-4 years AMD or Intel will be on more level grounds with nVidia so that I can finally stop giving them money just to have good ray tracing performance.