See an attached movie.

There are different accordions, and I start to open and collapse some of tabs. At some moment focused state is not applied (I mean, blue color stops to be applied).

Approximately, steps are (for any accordion):
Open tab0;
Collapse tab0;
Open tab0;
Collapse tab0;

And you can see, focused is not applied to any accordion on stage. This issue could be related to CSS issue, introduced in b13.