Published library not working, but works in modules

Hi,

I've been working on a little framework around my application - so far it's actually worked out pretty well, but I've hit an issue when I publish it and try to use it remotely.

The code is here: https://github.com/tanepiper/watchmaker-js - I've tried to configure the nx tooling as best I can, although I'm using their umd/esm builder it's configured with rollup to output for node.

The published file is here: https://unpkg.com/watchmaker-js@0.0.5/watchmaker-js.umd.js

Now when I try load this with require, I get an error - but if I take this file and put it in my modules directory it works fine can call it watchmaker-js.min.js it works fine!

The error is:

espruinotools.js:2872 Uncaught (in promise) SyntaxError: Unexpected character '§'

I was wondering if anyone had any experience with this, or might know what is causing this?

(And if you want to see how it's used - the app code is here https://github.com/tanepiper/BangleApps/blob/master/apps/moods/moods.js)