I need keep track of the status of WhatsApp API status notifications received via a webhook .

I built a stored procedure like this:

UPDATE wam 
SET
    [timestamp]=j.[timestamp],
    [status]=j.[status]

FROM WAMessages wam
JOIN  OPENJSON(@json)
WITH  (
         message_id     nvarchar(128)   '$.entry[0].changes[0].value.statuses[0].id' 
        ,[status]       nvarchar(128)   '$.entry[0].changes[0].value.statuses[0].status'
        ,[timestamp]    bigint          '$.entry[0].changes[0].value.statuses[0].timestamp'             
    ) j on wam.message_id=j.message_id

IF @@ROWCOUNT=0
    BEGIN
    
        INSERT INTO WAMessages 
        (
             message_id
            ,[status]
            ,[timestamp]
            --,other fields
        }
        
        SELECT 
            message_id
            ,[status]
            ,[timestamp]
        FROM OPENJSON(@json)
        WITH  (
                 message_id     nvarchar(128)   '$.entry[0].changes[0].value.statuses[0].id' 
                ,[status]       nvarchar(128)   '$.entry[0].changes[0].value.statuses[0].status'
                ,[timestamp]    bigint          '$.entry[0].changes[0].value.statuses[0].timestamp'
                --,other fields                 
            ) j 
    END

That works, but since 'sent' status message and 'delivered' status message are received simultaneously I get randomly only one of the messages to be processed:

Sometime I get only sent, sometimes only delivered:

There is a race condition issue I've not been able to solve:

I tried adding a WITH UPDLOCK or a LEVEL SERIALIZABLE and also using MERGE Statement, but nothing works:

clearly if I remove the UPDATE statement (and IF @@ROWCOUNT=0 ) I get 2 separated records, one for 'sent' and the other for 'delivered' statuses, but the target is to have only one record for each message_id with sent/delivered/read details.

Can suggest the right path to solve this issue?