The only recommendation we can advise for these symptoms is to try to uninstall and reinstall the application and make sure you have everything up to date on your phone.
Most of the time buffering occurs due to the device not receiving proper speed to be able to promote the video. If you're using Wi-Fi, it may be a bandwidth issue, or simple a priority setting you need to change on your router to get more speed to the phone.
If you're streaming utilizing data, it could be a situation where you are not in a good signal area, or data could be lowered by the carrier. Most carriers have a cap on how many GB can be used at a time before slowing the speeds down.
If you're still having symptoms appearing, try reaching out to your carrier or ISP for addtional steps.
