If I switch on the autorotate function, I noticed that the images are resized wrongly.

Is there some settings I should try to make it right or is this a bug?

Is this with all image or only some? Make sure that the internal/exif data about the image dimensions of the image are set correctly.

It is with all auto-rotated images. Only the full sized photo is not affected.

Ok my bad... is not with all images.. Will try and clear caches and see if that fixes it.

Ok fixed it by re-rotating the images. My guess is this kind of problem happens if you upload a photo with EXIF rotation and switch on the auto-rotate only after that.