Resuming a render issues

It seems that I am unable to resume a render with the movie render queue. The image always comes with artefacts.
I have the animation of a building growing, doors opening etc. I had to do some minor changes and now wanted to render just a portion of the animation… but it seems that the only way to get rid of artefacts is to render all 4500 frames instead of the 100 frames that I actually need re-rendered.
Am I missing something?