Hmm, I dunno. It could be anything, really. With young birds its really hard to tell, y'know? A lot of the times it's just because they are new to it, and others it may be because they are lacking in calcium.I'd imagine just getting interrupted while in the shelling phase could "interrupt" the smoothness of the egg.
If I get interrupted when I'm doing something I can't usually remember where I left off either.
You have a interesting concept, though.