Attempting to find understand/find specific examples of tactical failures and mishaps by General Lee and members of the Confederate Army throughout the battle of Gettysburg.
Im a little unsure what you mean by "surprise" in this context, could you expand on your question at all?
Were the Confederates "surprised" at Gettysburg? Not really, they knew they Union Army was hot on their heels and that a major battle was in the making for several days. Did most Confederate leaders expect that the fight at Herr's Ridge would lead to a more general engagement? Certainly not. Gettysburg was a meeting engagement in which both sides fought each other where they found them while sucking in more and more troops. In a tactical sense Lee was surprised that the Union Army was exactly where it was, concentrated as fast as it was, and was arrayed in the manner it was. It reflected a general lack of tactical intelligence as a result of JEB Stuart's infamous ride. But on a strategic level nothing about Gettysburg surprised anybody involved.
Well, insofar as "evidence" goes, if you only need one example all you really need to look at is Pickett's charge.
"Surprise" as we commonly think of it was really pretty rare in the ACW...it is hard to seriously surprise anyone when you have ten or twenty thousand man corps moving around open terrain at walking speed (aside: the handful of times armies were legitimately surprised, such as the Union XI corps at Chancellorsville, the results tended to be devastating).
The main reason for the ANV's consistent success prior to Gettysburg was they were able to concentrate combat power effectively at points of weakness or, alternatively, force their opponents to attack their positions of strength. They even did this successfully for the first two days at Gettysburg, to one degree or another. The third day though, they found the Union Army in an extremely strong position: elevated terrain, interior lines, numerical superiority, and so on. Instead of doing something unexpected, maneuvering to a position of advantage and then fighting from that position, Lee decided to conduct a frontal assault against a superior opponent in a superior position.
So, to the idea of "surprise": one of the largest artillery bombardments up to that point in human history informed the AoP exactly where the attack was coming, and then they had a solid mile of open terrain to cross, which at marching speed meant about 20 minutes of complete exposure while allowing the opponent plenty of time to reinforce the attacked position.