If your modem/router is using 2.4 GHz frequency instead of 5 GHz, the signal will travel farther but it will be slower, which could be causing buffering problems. Keep your router close to your main streaming devices and use 5 GHz for the best experience.

Can a bad modem cause buffering?

Old routers are guilty of both. Sometimes the software language isn't as modern as the devices that you're using, and sometimes the actual hardware itself can get frail and start to break down. Those old readings could result in your router's crappy bandwidth–leading to your huge buffering issues.

What is the most common cause of buffering?

Possibly the most common form of buffering occurs when your internet speed is too slow to download the amount of data needed. In this scenario, your device will buffer the data for the video and then begin playing it when there is enough data downloaded to prevent lag in the stream.