Im currently trying to upgrade my next js application to the latest version. To give you an idea of what the application uses custom webpack plugins to use less-loader and a file shadowing mechanism. I resolved all the type and linting issues and have adapted the webpack plugins to be compatible with webpack5. The application runs on a custom express server setup as described in the documentation.
Now I have been trying to debug this error:

TypeError: fetch failed
    at Object.processResponse (node:internal/deps/undici/undici:6323:34)
    at node:internal/deps/undici/undici:6648:42
    at node:internal/process/task_queues:140:7
    at AsyncResource.runInAsyncScope (node:async_hooks:203:9)
    at AsyncResource.runMicrotask (node:internal/process/task_queues:137:8) {
  cause: HeadersTimeoutError: Headers Timeout Error
      at Timeout.onParserTimeout [as callback] (.../node_modules/next/dist/compiled/undici/index.js:1:62578)
      at Timeout.onTimeout [as _onTimeout] (.../node_modules/next/dist/compiled/undici/index.js:2:269659)
      at listOnTimeout (node:internal/timers:564:17)
      at processTimers (node:internal/timers:507:7) {
    code: 'UND_ERR_HEADERS_TIMEOUT'
  }
}
HTTP 64193: server socket close
HTTP 64178: server socket close
HTTP 64178: SERVER new http connection
HTTP 64178: SERVER socketOnParserExecute 888
- error Error [TypeError]: fetch failed
    at Object.processResponse (node:internal/deps/undici/undici:6323:34)
    at node:internal/deps/undici/undici:6648:42
    at node:internal/process/task_queues:140:7
    at AsyncResource.runInAsyncScope (node:async_hooks:203:9)
    at AsyncResource.runMicrotask (node:internal/process/task_queues:137:8) {
  digest: undefined
}

but cannot get a stack trace and I do not receive any useful error response to debug what the issue is.
I have tried debugging with vscode and node but no results. If anyone has an idea on how I can approach this issue it would be much appreciated!!
Thanks!