Would need more information. What service are you using? What are your network settings? Are you hardwired or on wifi? What readings are you getting from a speed test?
Components in all boxes can fail at any time. Recently worked on a T1 original that had burnt out emmc storage. So it certainly can happen.
OP, did your problem resolve? Was it working good before? Any changes on your network since then? Internet speed? Downloading/uploading/streaming on other devices on your network @ the same time you notice buffering?