What do you do when grey rocking doesn’t seem to work?

My in laws constantly ask invasive questions. I’ve tried some versions of the grey rock approach. A lot of “I’m not sure” , “I don’t know” , classic “yes / no” with no elaboration. Trying to answer without giving an answer essentially. They really don’t get it. They either ask that same question another 3-4 times during that visit which I answer the same way or just continue with other questions trying to get every possible detail.

Some people may be comfortable sharing every detail of their travel plans, daily plans, parenting decisions, wedding decisions, etc but I often find the questions intrusive.

Sometimes it gets to the point where I want to shout, “can we talk about something else!” Or “it’s none of your business” they seem relentless or like they don’t listen. Is there any phrase that doesn’t seem rude but gets the point across?