Vercel.json being ignored? (React app redirects no longer working)

2 projects that we use vercel to deploy are experiencing the same bug. The index works on new deploys but the redirect does not. e.g. refreshing /dashboard in our app 404s but index is ok.

We did not tinker with our vercel.info file, the last working build was on 18th december. Today (22nd december) we deployed 2 applications and both had the issue. (They share similar configuration)

A day later, I managed to get something working by putting vercel.json in our /public folder.

This however feels weird because it is nowhere documented that it should be used like this. Anyone who knows what can be improved?

our CI does the vercel deploy step as such

- name: Deploy to vercel staging
    image: harbor.internal.azure.wegroup.be/dockercache/library/node:lts-alpine
    environment:
      VITE_SENTRY_DSN:
        from_secret: VITE_SENTRY_DSN
      NOW_TOKEN:
        from_secret: NOW_TOKEN
      NOW_SCOPE: wegroupwolves
      ALIASES: |
        customers.staging.wegroup.be
        customers.staging.wegroup.nl
    volumes:
      - name: cache
        path: /tmp/drone/cache
    commands:
      - npm i -g vercel@28.12.8
      - |
        NOW_DEPLOYMENT_URL=$(vercel -t $NOW_TOKEN \
        -S $NOW_SCOPE \
        -c \
        ./dist)