Hello fraubauer
When the ceiling formwork is set up, oil is sprayed on it so that the concrete forming the ceiling does not stick to the formwork. The oil must be removed before the ceiling is plastered. I don’t think the paint was applied directly to the concrete ceiling in your case. I would report this as a defect in writing and demand remediation, if the apartment is still under warranty. Normally, the plaster must be removed and reapplied. However, it might also be possible to generously remove the loose plaster and replaster just the affected area. But if the plaster is loose in other places as well, you’ll eventually have the same problem again.
Steven