Sum values in two different tables and join results keeping the columns

I have two tables: one with downtime and the other with productive time.

I want to have a table like this

But I am getting this

In the result, I am getting twice the downtime of the sum for the report 04102021-1, but as can be seen in the second picture, the value is present only once.
The script I am using is the following:

SELECT WAJ.REPORTCODE,--BASIC_REPORT_TABLE.TECHNICIAN,BASIC_REPORT_TABLE.JOBREPORTCODE,
    SUM(CASE WHEN DATEDIFF(SECOND,WAJ.TIMESTARTED,WAJ.TIMEFINISHED)<0 
     THEN (86400+DATEDIFF(SECOND,WAJ.TIMESTARTED,WAJ.TIMEFINISHED))/3600.0
     ELSE DATEDIFF(SECOND,WAJ.TIMESTARTED,WAJ.TIMEFINISHED) /3600.0
     END) AS PRODUCTION_TIME,
     
     SUM(CASE WHEN DATEDIFF(SECOND,WAS.TIMESTARTED,WAS.TIMEFINISHED)<0 
     THEN (86400+DATEDIFF(SECOND,WAS.TIMESTARTED,WAS.TIMEFINISHED))/3600.0
     ELSE DATEDIFF(SECOND,WAS.TIMESTARTED,WAS.TIMEFINISHED) /3600.0
     END) AS DOWNTIME
    
      FROM WORK_AT_JOB WAJ,WAITING_AT_SITE WAS

WHERE (WAJ.REPORTCODE=WAS.REPORTCODE AND WAJ.REPORTCODE LIKE '04102021%') GROUP BY WAJ.REPORTCODE

After the @xQbert comment, I tried this:

SELECT WAS.REPORTCODE,
    SUM(CASE WHEN DATEDIFF(SECOND,WAJ.TIMESTARTED,WAJ.TIMEFINISHED)<0 
     THEN (86400+DATEDIFF(SECOND,WAJ.TIMESTARTED,WAJ.TIMEFINISHED))/3600.0
     ELSE DATEDIFF(SECOND,WAJ.TIMESTARTED,WAJ.TIMEFINISHED) /3600.0
     END) AS PRODUCTION_TIME, 
     
     SUM(CASE WHEN DATEDIFF(SECOND,WAS.TIMESTARTED,WAS.TIMEFINISHED)<0 
     THEN (86400+DATEDIFF(SECOND,WAS.TIMESTARTED,WAS.TIMEFINISHED))/3600.0
     ELSE DATEDIFF(SECOND,WAS.TIMESTARTED,WAS.TIMEFINISHED) /3600.0
     END) AS DOWNTIME
     
      FROM WAITING_AT_SITE WAS 
      JOIN WORK_AT_JOB WAJ
      ON (WAJ.REPORTCODE=WAS.REPORTCODE AND WAS.REPORTCODE LIKE '04102021%') GROUP BY WAS.REPORTCODE

But I got the same result.
May you give some advice to get the result I want?
Thanks in advance

Answer

You could use conditional aggregation for this, but the easiest, and probably most performant, way to do this is to pre-aggregate the results before you join.

SELECT
  waj.REPORTCODE
  waj.PRODUCTION_TIME,
  was.DOWNTIME    
FROM (
    SELECT
      waj.REPORTCODE,
      SUM(CASE WHEN v.diff < 0 THEN 86400 + v.diff ELSE v.diff END / 3600.0) AS PRODUCTION_TIME
    FROM WORK_AT_JOB waj
    CROSS APPLY (VALUES( DATEDIFF(SECOND, waj.TIMESTARTED, waj.TIMEFINISHED) )) v(diff)
    WHERE waj.REPORTCODE LIKE '04102021%'
    GROUP BY
      waj.REPORTCODE
) waj
JOIN (
    SELECT
      was.REPORTCODE,
      SUM(CASE WHEN v.diff < 0 THEN 86400 + v.diff ELSE v.diff END / 3600.0) AS PRODUCTION_TIME
    FROM WAITING_AT_SITE was
    CROSS APPLY (VALUES( DATEDIFF(SECOND, was.TIMESTARTED, was.TIMEFINISHED) )) v(diff)
    WHERE was.REPORTCODE LIKE '04102021%'
    GROUP BY
      was.REPORTCODE
) was ON waj.REPORTCODE = was.REPORTCODE;

Note the use of CROSS APPLY (VALUES to avoid code repetition.