That is quite a high percentage. There are a few possible causes for malpositions, most of the time it's because the eggs were set incorrectly (pointy end up or slightly higher than the fat end) or inadequate/improper turning. Other possible causes are egg shell quality problems, the age of the hen who laid the eggs (higher occurrence in old hen's eggs), eggs stored too long pre-incubation (longer than 2 weeks), incorrect humidity during incubation resulting in incorrect air cell growth, incorrect temperature during incubation, improper feeding of breeding stock (too high levels of mycotoxins and vitamin/mineral deficiencies) and too low temperature during the last few days of incubation.
Just remember when you assist that if the chick did not pip into the air sac, but instead started with an external pip, you need to add the usual time between internal pip and external pip (roughly 6-7 hours) when you calculate when/if to assist. Best of luck with the hatch and I hope you can figure out what went wrong.
