Near the edge of a signal’s range, its performance and reliability can plummet as signal loss causes trouble. 5GHz has a much lower effective range than 2.4GHz

Near the edge of a signal’s range, its performance and reliability can plummet as signal loss causes trouble. 5GHz has a much lower effective range than 2.4GHz. Thus, there are areas where the 5GHz network will be available, but perform far worse than the 2.4GHz, even with congested 2.4GHz. (Still worse, in some devices it can cause persistent problems until reboot. My last laptop, a Surface Book, had a Realtek chip, and I was using it near the edge of a router’s range for hours a day last year, and every few days it’d get into a broken state where packet loss was >20% and latency a few hundred milliseconds, even if I moved right next to the router. Connecting to different networks wouldn’t fix it; sleeping the laptop wouldn’t fix it; disabling and reenabling the thing in Device Manager would normally but not quite always fix it; rebooting would always fix it.)