This seems to be specific to your app. The modal cannot load if you land directly to the app home /. It only works if you reload the page at /app/beads. Your app performs 302 redirect as soon as it lands on app home /. This is not a standard setup which could break when Shopify changes / tweaks how modal is loaded.
I think you have two options:
Option 1 (best): switch from ui-modal to use s-modal and s-app-windowModal
Option 2: continue using ui-modal but use 200 redirect on the client instead of 302 on the server