possible reasons

way out

processing
parameters

immoderate processing parameters

adjust chipload, rotate speed and feed speed

Discuss with technicians

immoderate negative press

moderate negative press

immoderate diameter of pressing tray

moderate pressing tray diameter

too much reshaping times

reduce reshaping times

too much hits

reduce hits numbers

PCB
physical properties

hard working materials

reduce layers and hits numbers

too much layers

reduce layer numbers

too much copper foil or too thick copper foil

reduce layers and hits numbers

unsuitable cover board

improve cover board qualities

drills
design

immoderate helix angle

increase helix angle to improve evicting speed

Try different drill types and check drills more carefully

too small flute

adjust drill shape including web, taper and flute

too small edge

increase the length of flute

immoderate tine angle or the first edge angle

improve sharpness by angle moderation

drills
qualities

low quality tip