Looks like dried mud with deep irregular cracks in the dry paint film.
MUD CRACKING CAUSES
Paint is applied excessively, making the film too thick for proper curing and drying. Trying to make one thick coat do when two regular coats will give superior performance. Allowing paint to build up in certain areas such as corners.
MUD CRACKING SOLUTIONS
Remove excessive paint in affected areas by scraping and sanding. Sand smooth and remove sanding dust before repainting. Prime if recommended and recoat with a top quality paint. The uniform spread rate should not exceed the manufacturer's recommendation.
PRIMERS & INTERIOR FINISHES
Priming is essential for better adhesion, sheen uniformity, mildew control and durability. Select a top quality interior paint in the color and sheen of your choice.