That can happen when this select returns more than one row;
and H.oh_name like (select oh_name,cast(V.OV_Value as varchar(50)) from OH H,OV V
where H.OH_NAME like 'DRE.JU.TASKSPAWN_JOB.P3'
and V.OV_VNAME like '&MASTERJOB#'
and H.OH_IDNR = V.OV_OH_IDNR
and H.OH_CLIENT = &$CLIENT#)
If it is always returning the same value, then just change "select" to "select distinct" to fix it. If it is returning more than one unique value, then you have a logical problem to figure out.