MacBook Air 13 battery drain issue following the Sonoma update

I'm using a 2018 Retina Macbook Air which has never had any battery issues before this update. It had roughly 50% battery when I shut the lid, and when I opened it this morning it was completely dead. It's running incredibly slow on startup as well for the last month or so, though I assumed that was age.

When I first started it and checked on my battery, it only showed me the first green section. It took until 15% charge and about 20 minutes for the second section to show up, but the second section isn't making ANY sense to me.

The laptop was asleep, in my bag and on the complete other side of the room from the charger, yet somehow it claims to be charging to full in the middle of the night? Is this a system glitch?

Is anybody else having any weird battery issues like this?

I've ruled out anybody else using the laptop since it is password locked and my fiance is a VERY heavy sleep so once he's out, he's OUT.

[Re-Titled by Moderator]