TC reported B-side cab door can be fullyopened but unable to fully close by itself. TC had to manua lly close cab door tightly. ~~~~~ 3668 TC reported B-side cab door can be fully opened but unable to fully close by itself. TC had to manually close cab door tightly. CE checked & found 3668 B/S cab door unable to open fully(electrically) and need to push either to open or closed.  3668 B/S cab door guide cleaned/cleared of any dirt & fine grains of sand. Cleaned J-bracket & function check - OK. Door able to fully closed/opened. Door monitor & DIR indications O  when cab door is fully closed.  Chan SW 44736