Static theme file is not copied to public when built with newer versions of hugo

Trying to run my site with hugo 0.43 (after using the env var workaround from #4851) results in a broken theme. 0.42.1 was also broken. My site works fine if I downgrade hugo to 0.40 (I happened to have this available in homebrew at the time).

When loading my site with the env var workaround and hugo server, I get the following message in the browser’s JS console:

Loading failed for the with source “http://localhost:1313/javascripts/modernizr.js”.

When running with 0.40, the terminal output shows “Static files | 80” but from 0.43 it shows “Static files | 67”, so some of the static files aren’t being picked up. I’m not sure how to dig into this further.

For reference, the theme I’m using is https://github.com/digitalcraftsman/hugo-material-docs and their example project (with minor tweaks: rename content/index.md to content/_index.md) works fine in 0.42.1 and 0.43.

Any suggestions on what might have changed recently that I should be updating in my config or anything like that?

Of course as soon as I posted I realized one major difference between my site and the example site: mine is set up to be bi-lingual. Removing all the information for the second language made it work with 0.43 so I’m guessing something changed in the language stuff in recent versions, which I still need to dig into.