Power off the laptop. Power it back on and when the ROG logo appears hold the power button in for 10 seconds. It should shut down again after a few seconds of holding the power button in. Now power back up normally and check your battery remaining in Windows.
See if this helps.
I already saw that suggestion somewhere, tried again just in case, no help 😞 Is there a chance that it's some motherboard issue? Specifically something related to charging circuit?