I’m having a similar situation with two different new Apple batteries. After dropping suddenly to 7% it eventually drops to 2% then eventually shows the final warnings and hibernates normally. Reset SMC and PRAM. Going to try NewerTech calibration steps. Hoping someone knows what causes this. Bad charging system?
These small connectors are delicate and very easy to break. Difficult to see while inside the case. A proper tool for removing and reattaching is required.
Beware that when you remove these screws the trackpad will have dropped down and resting on the screen. Maybe a precaution would be to place a thin cloth between the trackpad and screen.