I have had good luck heating the ferrule over an alcohol lamp and then imersing in ice water. Sometimes I need to repeat once or twice. Caution -- when heating you can build up considerable steam pressure, and when the glue finally lets go --BANG. Only a small dent in the sheetrock, but I am glad it wasn't pointed at the TV. Pins can be all but impossible to see. Try a light buffing w/ 0000 steel wool and a close inspection w/ srtong magnification.
AgMD