Honestly I'm not sure, I haven't given other eggs enough of a shot to compare. I've incubated some various mixed breed eggs but I feel like those have generally been really good at hatching perhaps due to hybrid vigor.
The vaulted skulls silkies can have probably don't help, I sometimes wonder if the large vaults contribute to certain malpositions.
What's your advice for breeding birds with vaulted skulls? Is it ok to breed two vaulted skulled birds together if neither has too large a vault? Or is it best to match a vaulted with a non vaulted?