Dålig lukt i diskmaskin!
Solved this finally. Culprit in my case was somewhat older plastic food containers (for keeping portions in freezer or taking lunch to work), which didn't really get clean. Fat from food would stick to the plastic regardless of detergent type. After I stopped putting plastic food containers, the smell never came back. Don't have to use the "best in test" detergent anymore either. No extra cleaning of dishwasher twice a week.
Food containers are now hand washed, zero problems. Will try with putting new containers just bought in there, to test. Plastic type must be of significance, I think.