Custom Instructions: Do they actually work?

Anyone recognizes this?.
Whatever I put in the custom instructions or telling ‘in-chat’ to keep in mind, just gets ignored.
Things like: “Give short answers”, “Don’t give any code untill asked for”, “Please talk English”, stuff like that.
If I put it in the ‘Custom Instructions’, it gets ignored all the same. If I remind ChatGPT ‘in-chat’ it works like 2 reactions and gets ignored again.
It should be an obvious thing to work but it’s very frustrating that it doesn’t .
It very much polutes every topic, with ChatGPT rambling on about things I dindn’t ask for.
Anyone have these same issues?