TC reported front DT 'A2' side train door not proven closed. TC opened and closed train doors 4 time s to clear fault. ~~~~~ L3 3603 A2 saloon door found no FOD. Checked door close force was at 8kg & door open force at 12kg. Checked & found dirt at J-rail. Cleaned up the dirt & further check on door close force was at 5kg & door open force was at 5.2kg. Function test door open/close operation - All OK (open at 3.3 sec & close at 3.3 sec).  Selvan/Lee PT. 23/06/2020.