AR posting fatal error

Hi,

1 user is currently encountering an error  in Production upon posting the group using the page below. This issue was not replicable in lower environment. As per checking the logs, there are some unique constraint error that might caused the issue. However, we're unable to trace how does PS_INSTALLATION_AR being populated. May we ask how this record works? or how the error below are being triggered? Thank you.

Error Position:  0   Return:  805 - ORA-00001: unique constraint (SYSADM.PS_POSTING_REQUEST) violated   Statement:  INSERT INTO PS_POSTING_REQUEST (OPRID, RUN_CNTL_ID, GROUP_BU, POST_FR_DT, POST_TO_DT, PROCESS_FREQUENCY, PROCESS_STATUS, PROCESS_INSTANCE, PROCESS_ORIG, LAST_RUN_DTM, PROCESS_U_HIST, PROCESS_P_HIST, PROCESS_D_HIST, SUBCUST_USE, CALC_YEAR, CALC_PERIOD, CALC_DATE_OPT, CALC_EFFDT, POSTNOW_TYPE, PREV_PROC_INSTANCE) SELECT 'SUSAN.KHO', 'RTM0005622', 'RWSPL', TO_DATE(TO_CHAR(SYSDATE,'YYYY-MM-DD'),'YYYY-MM-DD'), TO_DATE(TO_CHAR(SYSDATE,'YYYY-MM-DD'),'YYYY-MM-DD'), 'O', 'N', 0, ' ', NULL, 'N', 'N', 'N', 'N', 0, 0, 'R', NULL, 'P', 0 FROM PS_INSTALLATION_AR   Original Statement:  %InsertSelect(POSTING_REQUEST, INSTALLATION_AR, OPRID=%OperatorID, RUN_CNTL_ID='RTM0005622', GROUP_BU='RWSPL', POST_FR_DT=%CurrentDateIn, POST_TO_DT=%CurrentDateIn, PROCESS_FREQUENCY='O', PROCESS_STATUS='N', PROCESS_INSTANCE=0, PROCESS_U_HIST='N', PROCESS_P_HIST='N', PROCESS_D_HIST='N', SUBCUST_USE='N', POSTNOW_TYPE = 'P') FROM PS_INSTALLATION_AR PSAPPSRV.3632 (8388) 1-84    16.49.13    0.217000 SQL error. Function:  SQLExec