Custom Extension in Visual Builder - List page rule set not loading

Summary:

We have a custom object called ProjectTender. We ran the Extension Generator which created the required .zip file that we imported into Visual Builder:

https://docs.oracle.com/en/cloud/saas/sales/fasex/create-a-new-application-using-the-cx-extension-generator.html

Everything seemed to be working and we published the changes into the main branch and tested it working in the application after created a custom menu entry.

We identified that we needed to make some changes to our List page, so I opened our custom ProjectTender object in Visual Builder. Trying to modify the List Layout Rule Set now just keeps sitting there saying 'Loading fields'.