Your comments

Another way this can happen - it seemed to happen this way for me.

What I think happened is that I was on the 14th of 20 tabs on the list when Sidewise crashed (Aw Snap!!!).  Nothing happened immediately, but when I re-opened Chrome (SRW Iron), I noticed that the 14th tab had jumped to the 19th tab.

When I opened Sidewise, I saw the 14th tab hibernated (even though I never told it to), and the duplicate tab in the 19th position.

I couldn't unhibernate the tab, so I just moved the 19th one to the 14th position and deleted the hibernated entry.

What I am thinking happens is when Sidewise crashes, it hibernates the current tab and then tries to re-open it - which for me would be at the extreme right due to the New Tabs Always Last Extension.

But I see Aw Snap!!! so often it is almost unusable.