Powerline networking is a great example of where review sites totally fall down; it's amazing in most cases, providing great bandwidth and very low jitter and packet loss. Then for no reason*, it will absolutely suck for some people. The only way to find these kinds of problems is to survey every situation and test each product in all of them, which is clearly impossible.
People will hear this and go, "aha! Crowd sourcing!" The issue with that is that with modern technology the problem is overwhelmingly user error (or to be generous, perhaps UX). So you will spend essentially all your time chasing down people who don't know how to charge their product, or have their powerline adapter hooked up upstream of a UPS, etc
Your wiring is to blame. Maybe some staple missed and nicked the wire, maybe you have something leaking EMI, maybe you just have dirty power.