Flask error handlers not registered when defined in non-imported module with Gunicorn

When running a Dash/Flask application with Gunicorn, custom Flask error handlers (@server.errorhandler) are not invoked if they are defined in a module that is not imported by the module specified in the Gunicorn command. The server object passed to Gunicorn must already have error handlers registered at import time.

Ensure error handlers are registered in the same module that exports the server object being passed to Gunicorn (e.g., if running 'gunicorn index:server', define error handlers in index.py), or ensure the module containing error handlers is imported before the server object is exported. Verify the module initialization order matches the Gunicorn target.