I have found that it is problem of style img {max-width: 100%} if you have bar with most popular cheer. Overriding it fixed problem partially, because now as I noticed only moment when mouse is losing hover is moment of new message on chat. Unfortunatelly it’s for me almost impossible to debug JS of Twitch to find it. Additionally as I noticed on firefox problem doesn’t exist. Do you maybe know which js script is responsible for action at new message?