Below are a few external factors on why a Weigh Price Labeler might not be placing labels accurately.
Not all labels are created equal. Often times the labels do not separate from the backing paper as they should. This results in a poorly oriented label on the product.
One can often identify a bad label by looking at the underside of the backing paper. If the labels are die cut, you can often see a cutout of the label on the backing paper. This makes it much harder to remove the label from the roll.
Die cutting tools can put small amounts of label dust which can coat the surface of the labels. Label rollers on the inside of the labeler are responsible for straightening and aligning labels. When these labels run through, the dust on them can coat the rollers. Once this has happened, the dusty rollers are more likely to allow labels to slip and mis-align inside the labeler.
Bad Photo-eye to Product Match
Some products are domed or have irregular surfaces which can tell the photo eye to prepare the labeler at the wrong time. This might just take some trial and error to see the optimal level that the photo eye should be set at to allow the label to hit the product accurately.
In summary the labeling inaccuracies are not always a result of the machine. Careful attention should be given to the areas mentioned above.