I have the same experience as you. For me instructions in CLAUDE.md are followed almost always. On different projects, different CLAUDE.md files, some short, some long. No problem. When a specific instruction is skipped, I ask claude to emphasize it. It uses ALLCAPS, IMPORTANT!, etc., then it works 99% of the time. (Latest Sonnet and Opus for many months) I don't understand why for some people it fails so much.