I recently came accross an issue with Nintex Workflows 2013.
I'm using a workflow to create and update items in a SQL database, using BCS and secure store services.
Creating an item is OK, but I'm facing issue when updating items, and I'm not sure why.
I've double checked permissions at the BCS and secure store levels (ECT, external system, etc.).
From what I understand, and this worked on our 2010 environment with SPD workflows, I need to use the web applications pool account that I see in IIS.
Updating manually from the external list works fine, so it's definitely a permissions issue.
The sad thing is that I can't see anything in the logs, except maybe this one, which led me to think that maybe the "Update item" command was the problem (since I did test that I could find the item by ID using a "if" and a "log in history"):
Category is Legacy Workflow Infrastructure
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.SharePoint.SPListDataSource.UpdateEntityInstance(String bdcid, SPListItem itemToUpdate, IDictionary dictFieldValues)
at Microsoft.SharePoint.Workflow.SPWinOEWSSService.CommitUpdateListItem(Transaction txn, Object transData)
Any help would be appreciated, in the meantime I'll test with a SPD workflow instead.