You have to supply us with a whole lot more information. Your post is like saying ‘my car doesn’t work, please make it work’ without describing any of the symptoms.
You have this in the Scripting Support forum, so please post the script you are having issues with.
How much do you mean by ‘slightly move’? You may think 1 stud is slightly, while someone else might think .001 studs is slightly.
Are the Anchored Parts just moving once, or are they supposed to move controlled by your script but aren’t staying in one position when they are supposed to be stopped?
remember that if you select a model and anchor it there is a chance that parts of the model will not be anchored. maybe that causes the problem. What you should do is select one by one and put the anchor activated. Also, if it has a bodyVelocity or something like that, it would move because of that. or maybe a script that modifies the CFrame