When developing artworks that have being produced on my Photoplotter some images appear distorted or the line edges are not always sharp, how can this be prevented?

Mounting films to the raster of the  Fortex range of Laser Photoplotter must be carried out with considerable care ensuring after fixing the upper edge of the film to the drum, rotate the drum by hand and ensure the film is held tightly round the drum when fixed at the bottom.  It is is also very important to check that the Emulsion side of the Photoplotter Film is facing the drum.