After more than 15 years covering everything Apple, it’s with a heavy heart we announce that we will no longer be publishing new content on iMore and the iMore forums will be closing as of November 1st, 2024.
On iPhone5 and was having the same problem when watching videos on Facebook. Watching on YouTube was fast, using a 100m Internet connection so I'm sure it's fast enough. But when using Facebook, it just crawls and often not even buffering.
Recently I installed onavo count, removed it and everything was back to normal. Hope this helps.