Hi! Suprisingly not, Opera did the update to the 42.0.2393.137 this morning and every video is now playing fine oO. Well, thx for the pieces of advice, and long life to Opera! 🙂
I found a workaround by downgrading to Opera 41 changing my speed dial thumbnail then letting the auto update upgrade Opera back to the latest version of Opera 42 and the image I selected carries over.
I had a similar problem, try changing the mouse scroll speed through either control panel or settings app, it allows you to set how many pages scroll relative to moving the mouse scroll wheel.