Does that mean another action is required to switch to a non-cursed timeline? It became gray when Yuyuko was about to die, so I guess it's another event that will curse that new timeline Sakuya just opened.
Problem = opportunity. After all, she's the one who specifically has the power to change fate, if only she could be convinced that it was the best way to show her superiority.
The theory I've been running with this whole time was that Sakuya has been unable to time stop because her power is what was used to slide in the first place. She can't activate her powers while her power is already active, that is. Let's see where this goes.