What is your AI agent constantly doing wrong?

My colleague and I have found AI is consistently falling short on the following things. I'd be interested to know whether this is a prompting issue or a model issue (we use claude 4.7):

- comments being too verbose, and making reference to the previous code. Also just using phrases that no human would ever use (e.g. saying 'gate', 'belt-and-braces' a lot)

- over-using default arguments in method definitions

- failing to see the bigger picture in terms of DRYness, code organisation

- way too much defensive coding like handling edge cases that would never happen, adding fallbacks for everything