Air dried outdoors under cover, the equilibrium moisture content should be in the 12-15% range.
Indoors in service, that MC can drop as low as 4-5% and movement is probable. Particularly if the wood was cut tangentially, parallel to the plane of the growth rings.
The only fix that I've ever see was a set of ripping cuts, hidden on the underside of the wood, maybe 1/2 the thickness of the wood. That appeared to do a good job of alleviating the cupping movement.
A glue-up of narrow pieces works for this as well.