Cracking / Crazing

Usually associated with applying a fairly brittle paint over a highly flexible layer, i.e. matt over silk.

Solution

Rub down, correctly prime, i.e. Crown Trade Alkali Resisting Sealer and recoat.  For a water-based alternative, use PSB Stain Block Primer or Grip Extreme Fast Drying Primer.  Severe instances may require lining paper.