It's not because her vocals are bad, they're usually like that with her recent evo performances. It's because she forgot the lyrics a few times, had a few shortness of breaths, and she even apologized it at 7:20. It's probably that she didn't really practice for Evo because she performed it countless of times.
Ayu hasn't been in the media for quite some time.
I missed it when it was 24/7 & 365 days of the year of Ayu news.