I once (before ai) had a junior waste two months trying and failing to make a relatively simple change. As it turns out she it never occurred to her that she might want to copy the newly compiled executable ("it's the thing visual studio builds for you when you press build!" I had to explain this) to the server she was trying to run it on. So she never once managed to execute her changed code, which kept degrading as more and more changes accumulated trying to "fix" it