Forum is breaking back button

The longer I sit on this "create thread" page, the more history entries are created:

View attachment 29633

I've also seen the situation where there are only a couple of recent history entries under that back button, and everything older is gone.

I'm pretty sure it's related to ads, because these issues go away with an ad blocker. I'm running Firefox 54.0.1 on Window 10.

Forum is breaking back button