Battery light blinking, but battery still lasts for hours

I purchased a new battery for my N3DSXL from iFixit and did the required calibration of charging it all the way up, and then draining until it turns off, and charging it back up again, as suggested. After that, the battery lasts quite long, but the orange battery blinking light comes on on what seems to be half way before the battery actually dies.

I've repeated the calibration thinking it might have been that, but at this point I've done the calibration around 7 times, and the problem still persists.

When it's fully charged it correctly shows 100% charge, and it lasts for some hours before the blinking light comes and it is showing 5-1% by that point, yet I can continue to play for some more hours after until it shuts off.

Does anyone know or have any suggestions to what the problem might be?

I also checked with 3DSident what the battery voltage is after the light starts blinking, and it shows 3.4-3.3V, which from what I checked online should indicate empty battery, but then why does it still work for so long