[SalesForce] An internal server error has occurred. Error ID: 63354000-61927

Your trigger looks quite dangerous in that if ever two or more SO_Detail__c objects that are children of the same Outbound_Sales_Order__c parent are inserted or updated or deleted at the same time then the duplicate ID error will occur. (You may not expect that this will happen right now, but some upload or bulk update in the future may well cause that condition and bring proceedings to a halt.)

A way to avoid the error is to use a map keyed by the Outbound_Sales_Order__c ID and make some decision about which child object "wins". Making this change may work-around your test failures (which in some ways is a bad thing because why the failure is happening when the test only uses one SO_Detail__c is certainly unclear to me) and will make the normal production use of the trigger more reliable.

PS

This is how the map would be used to make sure there are never duplicate IDs when the update is done:

Map<Id, Outbound_Sales_Order__c> osos = new Map<Id, Outbound_Sales_Order__c>();

...

    Outbound_Sales_Order__c oso = osos.get(p.Outbound_Sales_Order__c);
    if (oso == null) {
        oso = new Outbound_Sales_Order__c(Id = p.Outbound_Sales_Order__c);
        osos.put(p.Outbound_Sales_Order__c, oso);
    }
    oso.x1_Issue__c = String.valueof(p.SOD_Issue__c);
    ...
...

update osos.values();

I think you need to use Tooling API instead.

I'm using JSForce for this.

connection.tooling.sobject('ApexClass').retrieve('01p7R000007Axk8QAC', (error, result) => {
   
});