My laptop shuts down unexpectedly (no BSOD) when i unplug it from wall power, and battery seems like it's dying

My Asus vivobook X540UA (windows 10) suddenly shuts down without warning (no BSOD) when I unplug it from wall power, however I can still use the battery if I turn it on while it's unplugged - but then the laptop randomly crashes doing mundane tasks. I used the Asus battery health charging utility and locked my battery's max charge to 60% 3 years ago because I keep it plugged in almost all the time (I know, bad habits die hard). I started seeing the problem around the summer period... I tried following guides to fix the problem but had no luck resolving the issue. The laptop now shuts down when

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