Error with GCP Dual Region storage bucket

[wekaso...@gmail.com]

I have set my storage bucket as dual region NAM4 (US-CENTRAL1 and US-EAST1) https://cloud.google.com/storage/docs/locations#location-dr while I have my cloud functions and everything else on us-east-1. When running a backup from a cloud function to this dual region bucket I am getting the following error:

Error: Bucket myapp-prod-backup.wekasolutions.co.nz is in location NAM4. This project can only operate on buckets spanning location us-east1 or us. at Gaxios._request (/workspace/node_modules/google-auth-library/node_modules/gaxios/build/src/gaxios.js

I want geo-redundancy.  It works if I use multi region but will this affect my costs?

The reason I chose Dual with NAM4 is it includes us-east-1 which I assumed meant I would not get charged for data transfer costs.