When deploying a solution to a destination source, it will fail on the last step with the error:
"Post-deployment error: Object reference not set to an instance of an object."
Please validate if the SharePoint 2013 Category has the correct name structure as the Package and deployment is dependant on this name during Deployment.
The script below can be executed to identify whether the Category Name is correct or not. If this is a K2 Cloud tenant you will need to raise this with K2 Support.
SELECT * FROM [Category].[Category] where Name like '%2013%'