Was the sin of Adam and Eve caused by partial ignorance? Before the fall they were ignorant about the shame of nakedness.
"Before the fall they were ignorant about the shame of nakedness." could better be described as innocent. Compare it with the situation of a young baby for instance.
But as for their first sin:
And the LORD God commanded the man, saying, “Of every tree of the garden you may freely eat; but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die.
— Genesis 2:16,17:
And the woman said to the serpent, “We may eat the fruit of the trees of the garden; but of the fruit of the tree which is in the midst of the garden, God has said, ‘You shall not eat it, nor shall you touch it, lest you die.’ ”
— Genesis 3:2,3
Clearly neither of them was ignorant that the fruit was forbidden. And they were well aware that the consequence of eating it (i.e. disobeying God) was to become subject to death.
Perhaps because there is no shame in nakedness when the people are sinless, that was why Adam and Eve felt no shame about their naturally naked state – until they sinned. Immediately, guilt afflicted them so that they felt the urge to use fig leaves to cover themselves, and to try to hide from God. God then considerately provided appropriate clothing out of animal skins: no doubt to help them cope with the chill winds and thorns outside of Eden.
However, the word ‘ignorance’ in the Bible is never applied to the One who “made everything that was made” (John 1:3) when he condescended to enter into our human state himself. “The Word was made flesh and dwelt among us” (John 1:14), his human mother, Mary, giving birth to him as a helpless baby. The record says that when he was 12 years of age, and returned from Jerusalem with Mary and Joseph:
“And Jesus increased in wisdom and stature, and in favour with God and man.” Luke 2:52 A.V.
A process had to be gone through, while in the flesh. And although physical growth was complete with Adam and Eve at the point of their creation, they had much to learn. We gather that Adam had learned enough about the animals to name them; to converse with God his Maker; to receive instructions about what he was to do, and what he was not to do. If he had been obedient to what he was not to do, he would not have then had to learn the hard way. If he had faith in God, that would have been sufficient for him to be obedient, without knowledge that came from a wrong, bad source and which cause him to learn the hard way – the wrong way.
Jesus is called “the last Adam”, contrasted with “the first man Adam” in 1 Corinthians 15:45, so the suggestion is that both of them were physically perfect and sinless (until the first Adam sinned, and the last Adam gave himself over to death without having sinned). And both of them went through the process of increasing in wisdom while on Earth, which does not entitle us to call them “ignorant”. On the contrary, Christ’s wisdom was unsurpassed, while Adam and Eve descended into ignorance as the inevitable process of alienating themselves from their Maker due to lack of faith to obey him.
To answer your question: Their sin was caused by lack of faith.
That’s a different way of looking at it, and I hope it’s helpful.
The shame of nakedness was only one of many things Adam and Eve were ignorant about, which might have contributed to the Fall. They did not know sin, for example. Eve did not know the pain of childbirth. Adam did not know the difficulty of earning his food by the sweat of his brow. They apparently did not know of murder or war, starvation or any of the other tragedies we normally think of as consequences of the Fall.
They also did not know death, at least not in the sense implied by "in the day you eat of it you shall die." (Gen. 2:17) They may have seen animals die but not humans, at least not as the story is written. This raises the question as to whether they understood that the same thing that the animals experienced could happen to them. Or perhaps they understood "death" in a spiritual sense. After all, they did not actually die for many years after they disobeyed. In any case, it seems obvious that if they actually did know the meaning of "death" (whether physical or spiritual) they would not have disregarded the warning.
We can add any number of tragic, shameful, painful or sinful things to the list. But certainly, their ignorance of the consequences of the Fall was a major contributing factor in their disobedience. For Christians and Jews alike, of course, ignorance of the consequences is no excuse for violating God's commandment. Among these consequences, shame about their nakedness is only one, and not the major one.