Hi Yifei,
I think is a problem with your transport. What options mark when use stms, the transport doesnt mark errors?.
IF _ls_supp-_18 EQ rs_c_false.
_curr_rule-ruleid = '18'.
* Step ID: '1', Type: 'CONSTANT'.
_curr_rule-stepid = '1'.
_G_1-/BIC/ZREGCOUNT = '1'.
ENDIF. "suppressed RULE