Laptop Battery Level dropping like a stone.

Hi. We have a Dell laptop which is around 2 years old. The device is only lightly used and the battery report still shows 94% capacity. The battery level drops normally to around 50% but then drops quickly to 4% and the laptop shuts down. I've tried calibrating the battery by fully charging and discharging twice but the problem still happens. Dell doesn't provide a calibration tool so charge/discharge is the only option.
I'm also told that the battery in this model (16 5625) isn't user replaceable and a chargeable service visit. Is needed. I would appreciate any advice on how to calibrate this battery other than what I've tried. Thanks very much.

Have you kept the Dell SupportAssist program on the computer? Or the MyDell app that can show something about the power?
Dell Support pages about the Inspiron 16 Notebook:

The battery is a gel-pac, harder to replace but not impossible, just have to remove part of the case.

P.S. I have Dells with both types of batteries used in Notebooks.

Hi Berton. Yes we have both Supportassist and My Dell apps on the PC. MyDell says battery health is excellent and the charging is set to Custom. The battery seems to be in good health but the battery level isn't being read properly. Thanks.