My capacitor is burt and I dont know whats causing it.

I was fixing an iPad for my friend and he told me that he left it overnight and the next day it won’t turn on, he brought it to a repair shop (not authorized), and they told him that somethings wrong with the battery, and they wanted to charge him over 450$. He declined and it was laying around for over 2 years. Yesterday he gave me this iPad for a repair and i agreed. Firstly i checked on the battery and it seemed ok, because the connector and the logic board started to heat up, it’s good to notice that the same repair shop replaced the screen on this iPad, and when i opened it up, there was missing screws, some brackets were just flying over the case. Luckily it doesn’t damaged the board or any component. Everything seemed fine so I wasn’t sure what is causing the problem, so I decided to search it on the internet, and there was a lonely post about the same issue with the same iPad Air 2 WiFi A1566. Some of the comments were saying that the power cord is damaged, but that wasn’t the case so I kept looking, and someone was saying that the charging port was broken so I cleaned it up and took it out of the case, checked it under the microscope and everything seemed good, so that still wasn’t the problem. Someone said that it’s the battery, and I was perturbed because I didn’t knew what was the issue, and finally found someone that said it could be a faulty motherboard, so i took it out of the housing, and decided to open it and check the internal components, Firstly i didn’t noticed it but then I saw a burnt capacitor. I thought to just replace it and it will be fine but I came with a thought that something needs to be causing it and the problem is going to come back, and I have a question for you, what can cause this problem?