If I open a saved project with pinned tabs restored from my last session, when I next run my solution the pinned tabs become unpinned. Is there a way to turn this behavior off? I pinned them for a reason and it is becoming quite frustrating as the solution grows.
I had the same problem and found the answer here
Go to Tools -> Options -> Environment -> Tabs and Windows and make sure "Maintain pin status if document is removed from well" is checked.