It can be avoided by:

1. Operator training (operator should instruct the enrolled person how to properly put the finger on the scanner)
2. A warning could be displayed by your enrollment software if the core/delta is not present on the image, or if core is too close to the border. (in this case, operator should re-enroll the finger.)
3. A warning could be displayed in your enrollment software if number of detected minutiae is too low. (in this case, operator should re-enroll the finger.)