What was the schedule that you followed that dropped the mc that much?
Many times, with oak, the surface damage is done within hours (minutes in the sun) after sawing. If I remember right, the surface must be kept free of air movement and almost the equivalent of being sprayed with water. It is tough to avoid surface checks in the initial stages of drying oak. Then as the drying progresses, the surface checks close and are never seen again until after drying is complete, and the finishing begins.