Tis the begging of the end.
It will eventually not charge at all.
It is not the battery, it is the circuit board responsible for charging in the controller.
Good luck, See other post about this topic.
The way I get arround it is I have a small 12V gel cell attached to a small 12v to 110vac inverter that I plug my power supply into which in turn is plugged into my controller. So I have to lump all this other gear arround when I want to fly.
I sent my P4 Pro controller in for service, twice, because the controller would not take a charge. First time, the battery was replaced and then returned ($190.). Battery ran down and would not take a charge. Returned for repair and the battery was replaced again. Also, the main board was ‘flowed’. Apparently this a common problem with the controllers. Haven’t had enough use to confirm the problem is fixed. I watched YouTube videos on the procedure to ‘flow’ the main board but didn’t feel comfortable doing it myself.