I hope this is the correct board, apologies if it is not.
I was fighting the lich in the cave on the Cloud peaks mountain. My fort save is 27 and I have a spellcraft rank of 30. He first cast Bigby's Clenched Fist, requiring a save of 32. The game used my basic score of 27 when rolling for a save, although I rolled high. It did not apply the +6 to saves.
He then cast Vampiric Feast and that did count my +6.

He then cast Bigby's Crushing Hand, which again did not give me my +6 to spells bonus. The roll was 27 v 32 instead of 33 v 32. I really only should have failed on a 1.

Is this usual? Do Bigby's ignore the spellcraft bonus? If not, what happened? It seems strange that I got the bonus from a spell like ability but not an actual spell from a spellbook. Is this a bug or a custom change of some kind?
Thanks.