Battery shuts down at 25%

Battery calibration being a myth was asked here Bought a new battery, do I need to calibrate it? - incidentally by you :-), so yes to repeat, it's a myth (see Izzy's answer that stressed this)

To address shutting down at 25%:

• If the battery is old or heavily used I would first change the battery




• Check if the behavior persists in safe mode. If it does go to next step. If it doesn't it's caused by some app you installed (unlikely)




• Do factory-reset. If it continues, flash stock ROM (updated if available) or custom ROM




• If none of these help head to service center get an estimate and choose between repair or replacement of the device