Repo graph gets distorted & hidden in chrome after a random mouse hover

When you go to repository and then graph (to see the branches and commits in a network graph) and then point the mouse randomly on any commit on the line graph, the display at the top part of the screen distorts and hides a major part of the graph. See image. This is repeated every time. It is highly annoying. I use chrome browser on a mac.

It seems there is some bug.
Has anyone else encountered this?