Sourcetree Tabs split up into separate windows on startup

With more than 5 repositories it makes only sense to use Sourcetree with tabs ("Merge all Windows"). Because with > 5 windows it gets really messy.

But there is one annoying bug:
Every time I close and reopen Sourcetree all the tabs split up into separate windows again. This bug requires me to click "Merge all Windows" every time after Sourcetree started.

This bug has been around for quiet some time now (more than 7 years!!) and has multiple issues (of which all of them are closed - which doesn't make any sense, since this bug has never been fixed!)
SRCTREE-4712, SRCTREE-4207, SRCTREE-4722

Please take some time to fix this bug, it would be really appreciated!

IMO: By default Sourcetree should open every repo in a tab (and not a window)