Hi Alexander,
as Thomas already said we need more details. If you use enblend for blending your images I am also interested in the command line arguments you provided. Can you share the .pto file with us?
Also did you add more images to the project than needed, e.g. are images overlapping almost completely? If that´s the case please try to deactivate redundant images (using the Fast Preview Window).
Does it work better if you change the order of images (in the Photos tab) so that the image in the affected part of your panorama is used earlier in the blending process?
Carl