Could be age, could be just wear and tear, could just be accidental mishandling of the laptop or charger. Many possible causes, and we won't know for sure unless we have someone like Louis Rossman look at it. He is a very smart repairman who has gone toe to toe with Apple in a courtroom, but he runs his own business and he's very busy.
While I may know quite a lot about laptops and PCs, unfortunately I don't know everything. I just know about the effects and symptoms of many issues from owning hundreds of laptops myself.
I'm very skilled with Dell and HP laptops, less so with MSI, ASUS, etc. General knowledge can often be applied across brands.