The charge rate slows down when getting to the last few percent. I’ve noticed that 13 does that from time to time when I use the Apple 20 watt. I just unplug it and plug it and it will top off. Now it could be that I’ve checked my phone too soon, I’ve never paid attention to how long my phone has been plugged in. I’ve never noticed it when plugged into the car usb or an old crappy multiport USB A (

) charger I have in the kitchen.
Just try unplugging and plugging it back in and giving it awhile. Or just leave it plugged in and see what happens.