The User Interface will display the following:
Error occurred while creating a new task
The event log will display Event ID: 0 with the following details:
A foreign key value cannot be insterted because a corresponding primary key value does not exist.
[Foreign key constraint name = FK_ADContainer_ADSyncTaskObjects]


The log may show the following:
Application: [Error, PID 4440, TID 8, SID, No Session, 18:13:39.021] Exception occurred while Adding new entries in ObjectsInfo and ObjectStatus for ObjectGUID:f5ae443c-43bf-43d1-a031-79aac4db62e4, ObjectEmail:, Exception:Parameterized query expects a parameter value which was not supplied. Parameter name: @Email StackTrace: at System.Data.SqlServerCe.SqlCeCommand.FillParameterDataBindings(Boolean verifyValue) at System.Data.SqlServerCe.SqlCeCommand.ExecuteCommand(CommandBehavior behavior, String method, ResultSetOptions options)
This issue can be caused when a user in Active Directory has whitespace for the Email address as pictured below:

This issue can be resolved by only selecting users who have a valid email address so that task creation completes successfully.
Or find the affected user(s) in Active Directory and resolve the white space issue for the email address.