Plot hole: Blofeld tells Bond that he realised he was not the real Sir Hilary Bray when Bond told him that the Bleuchamp tombs are in the Augsburg Cathedral. Blofeld informs Bond that they are in-fact in the Saint Anna Kirche, and the real Sir Hilary Bray would've known this. However Bond had gotten his information about the Bleuchamp tombs in Augsburg from the real Sir Hilary Bray earlier in the film. (01:19:05)
Other mistake: In the bobsled chase, Blofeld arms a grenade, which drops to the floor of his sled, where it rolls around with every turn. He arms and throws a second grenade onto the track, where it is detonated by Bond's sled. The original armed grenade loose in Blofeld's sled never detonates, even when that sled crashes.