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And just now in Gmail I opened the confirmation link for my account here. Gmail was the rightmost/bottom tab, and the link opened at the right/bottom, but not as a child, and Gmail moved all the way to the left and way up the sidebar, but not the top. It went in the middle of a bunch of suspended tabs. Opened another email link and it came up in the right place and as a child. Possibly I'm having a different issue. Using the dev channel.

This has been happening to me with no pinned tabs (never use them). Tabs also open to the left of the parent in the normal tab bar. Sometimes I'll be middle clicking a bunch of new tabs and most of them will open properly, but one or two go up/to the left. Sometimes I can open dozens of tabs and they all go fine. Sometimes I left click a link that opens a new tab and it does it. Keeps me on my toes. :P