Custom ./server/server.ts file with local imports keeps crashing

[markmals]

I'm working on a Remix app with several cron jobs defined in TypeScript files that import other TypeScript files. I need to initialize these cron jobs when the server starts, in the server.ts file, by importing and calling a TypeScript function. When I do this, set the server: "./server/server.ts" key in my remix.config.js, and run npm run dev, I get an initial Remix internal server error, followed by the server restarting, and a different error once I try to visit the localhost URL:

npm run dev output

npm run dev

> dev
> remix build && run-p dev:*

Building Remix app in production mode...
Built in 133ms

> dev:remix
> remix watch


> dev:node
> cross-env NODE_ENV=development nodemon ./build/index.js --watch ./build/index.js

[nodemon] 2.0.16
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): build/index.js
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node ./build/index.js`

/Users/orion/Developer/Playgrounds/remix-custom-server/node_modules/@remix-run/server-runtime/routes.js:18
  return Object.entries(manifest).filter(([, route]) => route.parentId === parentId).map(([id, route]) => ({ ...route,
                ^
TypeError: Cannot convert undefined or null to object
    at Function.entries (<anonymous>)
    at Object.createRoutes (/Users/orion/Developer/Playgrounds/remix-custom-server/node_modules/@remix-run/server-runtime/routes.js:18:17)
    at Object.createRequestHandler (/Users/orion/Developer/Playgrounds/remix-custom-server/node_modules/@remix-run/server-runtime/server.js:26:25)
    at createRequestHandler (/Users/orion/Developer/Playgrounds/remix-custom-server/node_modules/@remix-run/express/server.js:34:28)
    at Object.<anonymous> (/Users/orion/Developer/Playgrounds/remix-custom-server/build/index.js:42:46)
    at Module._compile (node:internal/modules/cjs/loader:1112:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1166:10)
    at Module.load (node:internal/modules/cjs/loader:988:32)
    at Function.Module._load (node:internal/modules/cjs/loader:834:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12)
[nodemon] app crashed - waiting for file changes before starting...
Watching Remix app in development mode...
💿 Built in 153ms
[nodemon] restarting due to changes...
[nodemon] starting `node ./build/index.js`
Express server listening on port 3000
Error: listen EADDRINUSE: address already in use :::3000
    at Server.setupListenHandle [as _listen2] (node:net:1422:16)
    at listenInCluster (node:net:1470:12)
    at Server.listen (node:net:1558:7)
    at Function.listen (/Users/orion/Developer/Playgrounds/remix-custom-server/node_modules/express/lib/application.js:635:24)
    at Object.<anonymous> (/Users/orion/Developer/Playgrounds/remix-custom-server/server/server.ts:44:5)
    at Module._compile (node:internal/modules/cjs/loader:1112:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1166:10)
    at Module.load (node:internal/modules/cjs/loader:988:32)
    at Function.Module._load (node:internal/modules/cjs/loader:834:12)
    at Module.require (node:internal/modules/cjs/loader:1012:19)
[nodemon] app crashed - waiting for file changes before starting...

Why is this happening? According to the documentation, I should be able to use a TypeScript file for the server file, when specified in my config, as I have done. Is it because it's nested in a /server directory? Is it because it imports another local TypeScript file?

I created a minimal reproduction of the issue, using the default Remix Express starter.