About a week ago the history buttons stopped working as they should in Safari. I've tested them in Firefox and they are still working there, and I've also checked my own Safari browser settings and they haven't changed.
Basically, you can't go back one move (it goes to the start of the match) and you can't then go forward one move or to the current stage of the game. You need to refresh the browser window to get back to the latest move. Essentially it means that you can't view any game history in Safari.