Perfectionism
Lex just could not help himself. There was a part of him that wanted to go down and work on the monument some more. He had thoroughly underestimated how much fun it was to create something, and his weird knack for perfectionism that he had thought disappeared made a comeback.
It was a strange trait he developed during his programming days. Sometimes, certain pieces of code would function, but would have theoretical limits or flaws. Any programmer worth his salt would just make a comment and just move on. Not Lex, though. He would have to find a way to fix the code so that it would work regardless of the situation.