One hearing aid stops charging and starts discharging in charger overnight (Philips 9040)

I have rechargeable Philips 9040s, purchased from Costco in December 2023 with the basic charger (the one that has to be connected to an electrical outlet, not the case with the battery in it). For a while I’ve been noticing that the left aid would (often but not every day) start getting low on battery far sooner than the right, even though the gain is similar so it shouldn’t be using more power. I wondered whether something was wrong with the battery. I quite often charge my aids overnight as I take them out just before bed and don’t have long enough in the morning to charge them before work. But then I noticed that the green light on the aid that indicates that the aid is fully charged when it’s still in the charger was quite often off on the left aid when I come to take the aids out of the charger in the morning, while it was still showing green on the right aid. So right aid = green light; left aid = no light. If I take the aid out of the charger and put it right back in again, it shows an orange light to indicate that it’s charging. So it seems that at some point during the night, the charger stops charging the aid and the aid goes into its active/on mode and starts discharging. So that would explain why the aid gets low on power earlier, as it has effectively been “on” for several hours before I actually start using it again. Has anyone else experienced this? Does anyone have any insight as to whether it is more likely to be an issue with the battery in the aid or the charger? If it’s the charger, I can probably ask Costco to give me a new charger, but if it’s the aid itself it will be a bit more complicated. Grateful for any thoughts.