Hi Keith,
Could you provide us data/table you are using to diagnosed issue in more detail.
In case of POSTALCODE geocode level, you might get error if other fields (like address) are mapped in output table. The workaround is map only postal code in output table.
We have a bug related to "postalcode" geocode level where geocode is failed when fields other than postal code is mapped in output table and its fix will be available in next patch (i.e. 17.0.2). you can use the workaround mentioned above for the time.