Hey there. We are also encountering issues. We have not gone live on prod yet but our staging app has been impacted since releasing a new version following the next gen migration.
Any attempt to hit a proxy route is met with a 404 and we do not see any request hitting out staging server.
We have then tried to release a prior version of the app which was working before, and even that does not resolve the issue.
We have also tried to test locally and are seeing the same issues.
This is a big blocker for us as its stopping us being able to make any deployments and are worried about the customer impact when we do go to release the next version of our production app. This is compounded by the fact that even rolling back to an older version of the app release does not seem to solve the issue.
Suggesting creating a new store and app doesn’t seem like an acceptable solution as we need to be able to test the behaviour of a release on our staging app before we can go to prod.