Chosen Solution
It started right after I plugged in the battery charger while I was playing (the light was red). I heard this popping/snapping sound and then it turned off. Now, whenever I fully open it, it turns off. So I’ve been playing with it opened 90 degrees. Could it be a problem with the speaker ribbon?
https://youtu.be/8UifkXEkV-0 See this video for details, it could be the speaker ribbon, but it might not be.