So after about 33.000 km on my odometer, my OBC stopped working. No error messages in the display though. Just a steady clicking sound under the hood when I connected the charger, and after about 1 minute, it stopped charging.
I drove to my dealership who confirmed problem with the OBC by reading error messages with the KDS software. Since this seems to be a fairly common problem, they had the part in stock, and 1,5 hours later, the OBC was replaced with a new one. I am really glad this happened in my guarantee periode.
I am really impressed with the service at my KIA dealership. Every time I report something, they take it seriously and fix the issue in a matter of days (except when they changed my instrument cluster, which took some time to receive). This far they have changed the right hand side mirror, the instrument cluster, the HVAC and now the OBC.
The service man (or whatever they are called) told me that the KIA producer takes all the information about occuring problem with specific parts seriously coming from KIA Norway, and the KIA producers seems to fix the problems on all cars produced just a couple of months later so the problem won't occur later on newer cars.