Battery draining and the 4rth led stays on

This just started randomly but I've had these headphones for at least 2 years. I just came back from a trip and they worked perfectly during the trip. I put them away when I got back and when I took them out (probably 2-3 weeks after) they had no charge which I thought maybe I left them on or with little charge. No problem I plugged them in and they worked fine.

I noticed that the 4rth LED on the battery indicator is on at all times. Regardless if they are on or off. This seems to be draining my battery. I had it fully charged yesterday. I turned them off and the next day they needed to be charged again.

I opened the side with the LED board and I found no burns or water damage.

Everything looked good but I ended up cleaning the board with 99% isopropyl just in case. No change.

I didn't test it further. Just put it all together and still working but the 4rth led for some reason is not turning off. Any ideas?