Question:

Why is the Pre_Call_Notes_vod field not getting updated on Calls?

Answer:

This behavior is expected if a specific sequence of Call creation takes place as seen below:

1. A first call is created and submitted with next call notes
2. A second call is created and submitted with updated next call notes
3. A third call is created (which will have pre-call notes visible) and submitted with updated next call notes
4. The second call is deleted
5. The third call will no longer have pre-call notes

Next Call Notes is pre-populated from the Next Call Notes value for the Call Report that is returned by the following query: 

SELECT 
(SELECT Next_Call_Notes_vod__c 
FROM Call2_vod__r 
WHERE Status_vod__c != 'Planned_vod' AND CreatedBy.Id = '[Current User Id]' 
ORDER BY Call_Datetime_vod__c DESC NULLS LAST, 
Call_Date_vod__c DESC NULLS LAST Limit 1) 
FROM ACCOUNT 
WHERE (ID = '[Account to Record the Call against]')

It returns the latest Call, but the user has to note that the query determines which one is the latest by the Call_Datetime_vod field, not the CreatedDate or LastModifiedDate fields. Currently, there is no out-of-the-box functionality in CRM to merge Calls. 

On new Calls, the Veeva code is used to auto-populate the Next Call Notes and not a trigger. It is currently not possible to extend this functionality to auto-populate fields.

Related Documentation:

Online Help Documentation: Using Pre-Call Notes and Next Call Notes