If your serratus anterior (SA) is strong, but your scapula is still winging, the problem might actually be the middle and lower trapezius and pec minor. If you are reaching forward with your arm, lifting something or pushing, serratus anterior and pec minor will activate. SA is trying to “push” (muscle only pull), move the scapula forward, and the pec minor will do similar and will medially rotate and anteriorly tilt the scapula, which lifts the medial border of the scap off the ribcage. If you are used to pulling heavy regularly, pull ups, rows etc, maybe you taught your body to retract the shoulder with mainly lats, rhomboids and upper trapezius, rather than also firstly laterally rotating and then gliding/sliding the scaps into spine with middle and lower trapezius. This lateral rotation + glidy movement if attempted when using SA and pec minor, will keep the medial border of the scap on the ribs. It’s a bit like anchoring it flat down. A sort of force couple activity to keep the scap on the ribs. Practice the GENTLE retraction, lateral rotation of the scaps, if you pull to hard you’ll use primary movers like lats. Gentler movement will get the smaller muscles going and will set up the scaps for a better solid, dynamic base and save you bad mileage on the shoulder joint.