Computer Failure problems of the 2004 Kia Motor Sedona

I have a 2004 kia sorento 4x4 (that car option not included in complaint form) one morning car started up rough and wouldn't stop. Engine light came on. Dropped off at dealership where they said it was my fuel injectors. They replaced them, but said they wanted to keep car overnight to make sure problem did not repeat. It started rough again with them and engine light came on again. They kept the car next day to dig deeper to find problem. They discovered the wire harness suffered a short and was burnt in 3 different areas. Since harness is connected from computer to spark plugs, fuel injector and other engine components they had to replace everything. . . But the computer. I got car back after 5 days. 2 days later car started rough idling and started misfiring and check engine light came on. I once again dropped car off at dealership. Said it feels like the same problem, or could be related to work done. They said random misfires are common and cleared computer log and I got car back. Next morning car ran rough again and was misfiring again. I called kia service and said that this car never misfired before or ran rough and how can a random misfire happen so frequently and isn't it coincidental that it only started happening after my wire harness suffered from a short that was directly attached to the spark plugs. Service manager mention that technician working on car thought that computer was malfunctioning but neglected to tell me. I asked if they knew it was malfunctioning, why did they ever give the car back till everything was fixed. He said they need proof and not just maybe's. I told them that the constant misfiring was proof enough. They took the car back and replaced the computer. They sent the computer to kia headquarters to investigate why the computer malfunctioned. I was told that they were worried that this may not be a isolated case.