Row 2: ORA-04091: table SUMMITTEST.APL_LOG is mutating, trigger/function may not see it

Having looked at the following Trigger, still getting the Row 2: "ORA-04091: table SUMMITTEST.APL_LOG is mutating, trigger/function may not see it" error, Please can anyone provide any help in resolving this?

create or replace TRIGGER SUMMITTEST.NEW_APP_TEST AFTER INSERT ON SUMMITTEST.APL_LOG
FOR EACH ROW  WHEN (new.APL_CO='01' or new.apl_co='40') BEGIN 
INSERT INTO SUMMITTEST.WEPALERT select 
             9,               --EVENT_ID
             1,                     --EVENT_NO
              SYSDATE(),              --ACTION_DATE
              'EVENTS',               --ACTION_USER
              DECODE(JTT_EXTRA1,'','cjohnson300@hotmail.com',jtt_extra1),                 --COMM_X_1
              '',                     --COMM_X_2
              '',                     --COMM_X_3
              '',                     --COMM_X_4
              '',                     --COMM_X_5
              '',                     --COMM_X_6
              '',                     --COMM_X_7
              '',                     --COMM_X_8
              '',                     --COMM_MESSAGE
              '',                     --COMM_PRIORITY
              :new.APL_COMMENT,                     --COMM_SUBJECT
              :new.APL_CO,             --X_REF_1
              trim(substr(:new.apl_source_key,3,16)) || ' - ' || cla_name contract,           --X_REF_2
              to_char(:new.apl_value,'99,999,999.99') newnum,               --X_REF_3
              substr(:new.apl_source_key,-8,8) order2,          --X_REF_4
              decode(olr_url,'','','This is an amended order.  To see the previously approved order, click'),           --X_REF_5
              decode(olr_url,'','',' <a href=' || olr_url || '>here</a>'),              --X_REF_6
              bxs_name,                 --X_REF_7
              poh_pla_no2 || ' - ' || pla_name,                     --X_REF_8
              to_char(poh_order_date, 'dd/mm/yyyy') order_date,                     --X_REF_9
              :new.apl_value,               --N_REF_1
              :new.apl_co,                  --N_REF_2
              0,                    --N_REF_3
              0,                      --N_REF_4
              0,                      --N_REF_5
              0,                      --N_REF_6
              0,                      --N_REF_7
              0,                      --N_REF_8
              0,                      --N_REF_9
              SYSDATE(),            --D_REF_1
              SYSDATE(),                     --D_REF_2
              SYSDATE(),                     --D_REF_3
              SYSDATE(),                     --D_REF_4
              SYSDATE(),                     --D_REF_5
              SYSDATE(),                     --D_REF_6
              SYSDATE(),                     --D_REF_7
              SYSDATE(),                     --D_REF_8
              SYSDATE(),                     --D_REF_9
              0,                      --EXCLUSIVE_PROC
              0,                      --ALERT_PROC
              0,                      --NOT_COMM_COUNT
              0                       --POOL_ID
FROM SUMMITTEST.APL_LOG 
left join 
(select apr_co, apr_stage, apr_user from SUMMITTEST.apr_rule where apr_type='PO' and  apr_subtype=' ' and substr(apr_user,1,1)='%') c on 
c.apr_co=apl_co and apl_stage+1=apr_stage
left join 
(select ana_co, ana_type,ana_no, jtt_name, jtt_extra1 from SUMMITTEST.ana_anal left join SUMMITTEST.jtt_tab on jtt_co=ana_co and ana_code=jtt_no) d 
on d.ana_co=apl_co and d.ana_no=trim(substr
(apl_source_key,3,16)) and d.ana_type=substr(apr_user,-3,3)
left join SUMMITTEST.poh_hfm on poh_co=apl_co and poh_contract=trim(substr(apl_source_key,3,16)) and poh_order2=trim(substr(apl_source_key,-8,8))
left join SUMMITTEST.bxs_sec on bxs_menu=poh_buyer and bxs_type='U'
left join SUMMITTEST.cla_acc on cla_co=apl_co and cla_no=trim(substr(apl_source_key,3,16))
left join SUMMITTEST.pla_acc on pla_co=poh_co and poh_pla_no2=pla_no
left join 
(select olr_url, olt_id from SUMMITTEST.olr_res
right join
(select max(olt_res_id) link_me, olt_id from SUMMITTEST.olt_tre group by olt_id) a on a.link_me=olr_id) b on poh_ole=b.olt_id 
WHERE :new.apl_id=apl_id and :new.apl_time=apl_time and (:new.apl_stat_x =' ' or :new.apl_stat_x='N') and :new.apl_type='PO';
END;