Hot corners changing too rapidly on my MacBook Air

This is a random question, but my hot corners used to sort of fade out, like you could see the windows dragging out to the desktop. Suddenly the active window just disappears and the desktop appears when I drag to the corner. It's weirdly jarring and I'd like to turn it back to how it was. I've probably done this myself as I was trying to change my display setup but I have no idea what I have changed or how to change it back. Any suggestions please?

[Re-Titled by Moderator]