Project Site - Navigation link broken on Project Detail Page

Hello Ana-S ,

This is by design as the Project Details links are added by the Project Server Project Site provisioning process. To get around this, you need to update the navigation post site creation. You can either do this manually or write code to do it. You could automate all of this if you wanted, trigger your custom code to run on the site created event in SharePoint. The SharePoint PnP remote provisioning could be an option: https://learn.microsoft.com/en-us/sharepoint/dev/solution-guidance/pnp-remote-provisioning 

Paul