I think this is the same issue as I'm trying to fix right now.
On forums, they often have a preview function if you hover over the thread title. This is working for me on some forums, but not on one specific one that I use daily.
Oddly, its working on my work PC and it worked on my desktop PC that I sold last week. But not working on my Surface Pro. I've completely uninstalled Opera and all the local data, and reinstalled - no difference.