we never worked out why dd couldn't/wouldn't open her mouth wide, 2 very experienced bf advisors and the lactation consultant at our mat unit took a look and couldn't give us an answer!
Was truly awful for a while esp as her weight gain was poor, but she sorted it out herself in the end
now at 9mths she can give me love bites the size of 10p bits on my boobs if she aims wrongly!!