Damage to the valve caused by continuous banging against the retainer.
Install the Sonnax 3-2 shift timing valve kit to restore proper function.
In Ford AXODE, AX4S units, the small diameter front spring stem of the aluminum OE 3-2 shift timing valve impacts the thin steel retainer when stroked. The force of this constant hammering can damge the thin OE retainer. Once the retainer is damaged the valve can be side loaded, which may bend the valve and cause it to stick or even seize in the bore. The Sonnax 3-2 shift timing valve kit 96201-29K will restore proper function.