Hard Wired Doorbell Won’t Charge Anymore

We have 9 Video Doorbells. Two of them (one an original model and the other a model 2), each about 3 years old, are hard wired to Ring power supplies and no longer charge. I can charge them on a USB charger to full but that charge only lasts about a week or 2. I see there are after-market batteries available that even come with a special tool to open them. I bought a new Ring doorbell and replaced one of them with it, proving the power supply is just fine. The other I need to decide whether to try to put a new battery in or replace the doorbell. Why are these units failing so early? It is very disappointying.