Symptoms

"Object reference not set to an instance of an object" error occurs when trying to deploy objects with the type - "field" from package using K2 Package and Deployment utility. Also Package and Deployment utility fails to detect that some fields in the package already exist in the target environment.
 

Diagnoses

As a part of troubleshooting/investigation you may run the following stored procedures:
Environment.GetEnvironmentData
Environment.GetFieldTypes
Environment.GetFieldAndFieldTypeByFieldName
And check what they return. Described symptoms may be a result of missing Environment.GetFieldAndFieldTypeByFieldName stored procedure in the target package deployment environment.
 

Resolution

In case one of the stored procedure is missing you may recreate it by copying from other K2 environment with the same version of K2 components installed. Note that K2 database backup is necessary before attempting to perform any direct changes to K2 database. If you not entirely sure how to perform this operation you may log a support ticket with K2 support.