MagSafe charger draining battery after charging to 100%

When Charging my iPhone 12 Pro with a MagSafe charger over night, it will charge to 100% and then begin draining my battery all night. I wake with my phone at 50% charge. If I wake and find it has begun draining, I can lift the phone off the charger and replace it and it will begin charging back up quickly as it should. I have tried my wife charger and have the same result.

If I use the lightning port it will charge up to 80% and trickle charge the remaining 20% and then maintain.

I kept thinking it was me not putting it on the charger correctly. Finally I checked the battery app and found the issue was not me but the charger. I also notice that this has already reduced my battery health down to 89% of capacity in just 9 months.

Below I have attached an image of the battery charging. As you can see I started charging around 9pm. It becomes fully charged by about 10ish. I wake and see that it has been draining. I remove and replace the phone on the charger and it begins to charge immediately.