Why does the gypsum board ceiling of the wooden keel crack

I'm doing home improvement, I'll tell you. Wood itself has an elasticity, and it will crack or deform and bend when it is damp or something. Drywall is also not resistant to moisture, and cracking is only a matter of time or time.

Although the light steel keel is not as easy to deform as wood, the gypsum board may not be firmly fixed with the light steel keel, so that the plate produces internal force, and the shear at the joints of the plate causes deformation and cracks; The stiffness and straightness of the light steel keel are not enough, and the spacing is improper, which will inevitably produce deformation and cracking.