not a single-group group function

WITH practice AS
(select max(semester) semester, planid, activitytypeid,sum(weeks) weeks
                FROM pl_specialworks
                group by PLANID, ACTIVITYTYPEID
                )
SELECT decode(1,1,ap.semester,0) semester, PS_RETURNRECDISCIPLINES(r.recordid) displan, r.zet,  
            (case when EP.STUDYFORM in (4,5,11) then r.zet_hours*r.zet else r.hourstotalamount+nvl(r.reattestation,0) end)||'ч' hoursPlan,
                      (CASE WHEN ap.exam1_present=1 THEN 3  WHEN ap.exam2_present=1 AND dz.semester IS  NULL THEN 4
                           when AP.EXAM2_PRESENT=1 and DZ.SEMESTER=AP.SEMESTER then 49 end) ACTTYPEPLAN,
                        NVL2(CD.STUDENTDISCIPLINEID1, SD1.DISCNAME||(case when SD1.HOURS > 0 then', '||SD1.HOURS||' ч' end)||DECODE(SD1.ACTIVITYTYPE,3,', экзамен',4,', зачет',49,', диф. зачет','')||'; ','')||
                        NVL2(CD.STUDENTDISCIPLINEID2, SD2.DISCNAME||(case when SD2.HOURS > 0 then', '||SD2.HOURS||' ч' end)||DECODE(SD2.ACTIVITYTYPE,3,', экзамен',4,', зачет',49,', диф. зачет','')||'; ','')||
                        nvl2(cd.STUDENTDISCIPLINEID3, SD3.DISCNAME||(case when SD3.HOURS > 0 then', '||SD3.HOURS||' ч' end)||decode(sd3.activitytype,3,', экзамен',4,', зачет',49,', диф. зачет','')||'; ','') DISSTUD,
                        cd.reattestation, cd.hourssave, cd.zetsave,
                        decode(cd.activitytype,3,'экзамен',4,'зачет',49,'диф. зачет','') atypesave,
                        ed.docname,decode(r.disccycle,6,99,23,99,r.disccycle),decode(r.component,5,7,7,6,6,5,r.component) component, r.recordno, r.recordname, d.name, wm_concat(distinct(cmp.ind)) comp,
                        R.DISC_CODE CODE                       
FROM pl_planrecords r
left join pl_educplans ep on ep.planid=R.PLANID
left join IP_COMPLIANCEDISCIPLINES CD on R.RECORDID=CD.RECORDID and CD.STUDENTID=4861
left join ip_studentdisciplines sd1 on sd1.STUDENTDISCIPLINEID=cd.STUDENTDISCIPLINEID1 
left join IP_STUDENTDISCIPLINES SD2 on SD2.STUDENTDISCIPLINEID=CD.STUDENTDISCIPLINEID2 
left join IP_STUDENTDISCIPLINES SD3 on SD3.STUDENTDISCIPLINEID=CD.STUDENTDISCIPLINEID3
left join ip_educdocuments ed on ed.docid=sd1.docid
left join RB_DISCIPLINES D on D.CODE=R.DISCID
left join pl_cycles c on c.code=r.disccycle
left join pl_competence cmp on cmp.planid=ep.planid
left join (select pa.recordid, exam1_present,exam2_present, pa.semester
           from pl_plansemesters pa 
           WHERE  pa.semester = (SELECT MAX(semester) FROM pl_plansemesters pa1 WHERE pa1.recordid=pa.recordid)
           ) ap ON ap.recordid=r.recordid and r.recordid=ap.recordid
LEFT JOIN pl_dif_zachets dz ON dz.disciplineid=r.discid AND dz.planid=r.planid AND dz.semester=ap.semester
left join ( select recordid, sum(zet) zet
                    from pl_plansemesters group by recordid) ah on ah.recordid=r.recordid
WHERE r.planid=8879 and (0=0 or (1=0 and cd.recordid is not null))
and r.modular=0
union all
select decode(1,1,s.semester,0), a.name, null, nvl(s.weeks,0)||' нед',s.activitytypeid, spr.discname, spr.reattestation, null, round(spr.weeksave*3/2),null, ed.docname,
      null, null, null, null, null, null, null
from practice s
JOIN tt_activitytypes A ON A.activitytypeid=s.activitytypeid
left join ( 
    select CP.PLANID, CP.ACTIVITYTYPESAVE, SD.STUDENTID, SD.STUDENTDISCIPLINEID, cp.reattestation, cp.weeksave, sd.docid, sd.discname 
    from IP_COMPLIANCEPRACTICE CP
    left join IP_STUDENTDISCIPLINES SD on SD.STUDENTDISCIPLINEID = CP.STUDENTDISCIPLINEID 
) spr on spr.PLANID = S.PLANID and spr.ACTIVITYTYPESAVE=S.ACTIVITYTYPEID and spr.STUDENTID = 4861
left join ip_educdocuments ed on ed.docid=spr.docid
JOIN PL_EDUCPLANS EP ON EP.PLANID=S.PLANID
where S.PLANID=8879 and S.ACTIVITYTYPEID in (18,57) and ep.yearbegin < 2018
order by 1,12,13 desc,17, 14,15,16