Discovered system freezing up from piston to evaporator coil. Had stuck piston in straight cool package unit. Added a shot of refrigerant to try and get the piston unstuck. Successfully unstuck the piston for now. Thawed out evaporator coil. Confirmed proper operations. Verified all ductwork underneath home looks good. Left estimate to recover. Refrigerant flush out system. Replaced filter dryer and clean piston if issue reoccurs. System is operating properly at this time.