The tip using the force rewrite title helped me on my subpages and posts. But at homepage, were my latests posts are listed, I do have the title still twice. I do not have any intention rewriting the code of my theme, because if it gets updated, I have to do it again – a pain, if I forget it.
It would be nice, if Joost will update his plugin in short time, because this is the reason for this bug.