The past several weeks, I often come across tabs that don't load. All I see is that spinning circle. I must close the tab, and reopen it, usually with my Undo Closed Tabs addon. It also often happens with multiple adjacent tabs. I have this tab manager, and If I open the window the tab list, the icons of several of the the tabs below the tabs that won't load are spinning, even tho they haven't been selected yet, and I must repeat the close/open process. It's like a chain reaction. When one tabs is closed and reopened, it prompts other to repeat the behavior. After a while it stops. There's really no pattern. I never know when it's going to begin.