The Great Pyramid blocks were installed (or with the bulk of them mixed like concrete), but during construction there was a bad quake which left the corbels at the top of the Grand Gallery hanging on at one end a mere fraction of an inch.
It was at that point the relieving chambers were accessed (a small tunnel was chewed through) to inspect the damage. Those slabs were cracked, but as the pyramid was nearly complete (or was complete) nothing could be done. They bet right, it’s still there.
Jean-Pierre Houdin and his consultants attributed the cracking to softer strata under one side of the foundation level, if memory serves.
