scrolling down runs out of posts Twitter

When Im on twitter or Facebook just checking todays posts etc.

As I scroll down I get so far then it runs out and just goes blank. And I cannot scroll any longer or back up and just get the spinning ball of doom.

Even if I refresh the page by highlighting the url as I can't with the spinning beachball, sometimes it refreshes ok but I can still only get so far down or Sometimes it refreshes but stays the same with the beach ball again and the only way I can get back in is to re-click my shortcut in my favourites so it completely comes out of the twitter/facebook site and then loads a fresh one but again can only get so far.

It is also happening on some sites i:e Jyf tv when I try to do a search for a movie, some times it works fine sometimes it doesn't and again the beachball, and again I have to completely come out.

I have tried clearing my history and cache and also deleting the com.apple.safari.plist file and restarting.

I have already re-set safari which it was still doing it before I did this.

And I have tried repairing permissions.

I have checked any extensions and I have done a run with malwarebytes.

I am running a mid 2009 (pretty old now) macbook pro

Yosemite 10.10.5

Safari 10.1.2

Thanks for any replies