I am re-painting my home ceilings.....have not been painted in 10 years.
I am using Dutch Boy ceiling paint......my problem is....as I am painting, the old paint ( in some area's) is coming off onto the roller as I apply the new paint.
I have painted many times in my life....never ...ever had this problem.
you may consider getting one of those really rough bathroom scrubbers, you know those black scrubbies and run it over the ceiling somewhat lightly. it will pull up the loose flake. you then wipe the ceiling down with a wet towel, inspect to make sure you didn't leave any deep scratches and paint.
if the old stuff is coming off you have to deal with it. if you don't there's a good chance even if you go over it paint cracks will develop since the new stuff is stuck to loose old paint