Dev Server Issues?

Just posted to Discord:

I'm working on my personal site, and am using 11ty with Tailwind and DaisyUI, and have a frustrating problem.

Most pages and posts call on default.njk, which is my main layout.

I'm trying a lot of small variations in the styling at the moment due to how Tailwind works, but the changes to default.njk are not coming through to /_site.

The dev server is seeing the file change, and thinks it has overwritten the file.

[11ty] [11ty] File changed: src/_layouts/default.njk 
...
[11ty] [11ty] Writing _site/index.html from ./src/index.njk
...
[11ty] [11ty] Benchmark    242ms  73%   676× (Configuration) "slugify" Nunjucks Filter
[11ty] [11ty] Copied 2 files / Wrote 44 files in 0.33 seconds (7.5ms each, v2.0.1)
[11ty] [11ty] Watching...

but nothing changes in the html. I've checked the generated html via nano, so know it's not caching in FireFox. If I delete the /_site folder and restart 11ty it all works fine.

I've checked all the permissions, and everything looks OK.

11ty version is 2.0.1, running on my debian 12 server.

npm doctor
Check                               Value   Recommendation/Notes
npm ping                            ok
npm -v                              ok      current: v10.3.0, latest: v10.3.0
node -v                             ok      current: v20.11.0, recommended: v20.11.0
npm config get registry             ok      using default registry (https://registry.npmjs.org/)
git executable in PATH              ok      /usr/bin/git
global bin folder in PATH           ok      /usr/local/bin
Perms check on cached files         ok
Perms check on local node_modules   ok
Perms check on global node_modules  ok
Perms check on local bin folder     ok
Perms check on global bin folder    ok
npm WARN verifyCachedFiles Content garbage-collected: 162 (64655765 bytes)
npm WARN verifyCachedFiles Cache issues have been fixed
Verify cache contents               ok      verified 4259 tarballs

package.json contains:

"main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start-run-old": "npm-run-all -p dev:*",
    "start": "concurrently \"npm run dev:*\"",
    "dev:11ty": "eleventy --serve --port=4004",
    "dev:tw": "tailwindcss -i src/assets/css/tailwind.css -c tailwind.config.js -o _site/assets/css/tw-style.css --watch",
    "build": "ELEVENTY_PRODUCTION=true eleventy && NODE_ENV=production npx tailwindcss -i src/assets/css/tailwind.css -c tailwind.config.js -o _site/assets/css/tw-style.css --minify"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@11ty/eleventy": "^2.0.1",
    "@11ty/eleventy-plugin-syntaxhighlight": "^5.0.0",
    "@tailwindcss/typography": "^0.5.10",
    "autoprefixer": "^10.4.16",
    "concurrently": "^8.2.2",
    "daisyui": "^4.6.0",
    "npm-run-all": "^4.1.5",
    "postcss": "^8.4.33",
    "tailwindcss": "^3.4.1"
  }

Even just running npm run dev:11ty isn't changing when I change comments in the default.njk.