How to debug issues on Vercel?

[simmbiote]

How can I determine the underlying issue for something that is happening on edge-runtime only?
In vercel logs I see this:

ReferenceError: self is not defined
    at Object.<anonymous> (/var/task/.next/server/pages/s.js:1:1)
    at Module._compile (node:internal/modules/cjs/loader:1256:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1310:10)
    at Module.load (node:internal/modules/cjs/loader:1119:32)
    at Module._load (node:internal/modules/cjs/loader:960:12)
    at Module.require (node:internal/modules/cjs/loader:1143:19)
    at Hook._require.Module.require (/var/task/___vc/__launcher.js:2160:44)
    at require (node:internal/modules/cjs/helpers:121:18)
    at requirePage (/var/task/node_modules/next/dist/server/require.js:156:12)
    at /var/task/node_modules/next/dist/server/load-components.js:68:84 {
  page: '/en/s'
}
RequestId: ----- Error: Runtime exited with error: exit status 1
Runtime.ExitError