Enabling vendor in deno.json results in esbuild errors

[A1029384756]

I am attempting to package a Fresh application with Nix which disables all internet access at build time. As a result, I vendor my dependencies by setting "vendor": true in deno.json. Once this is done, I get the following error:

✘ [ERROR] [unreachable] Not an ESM module. [plugin deno-loader]

in multiple spots. Is that something that is known or is more work needed to find the source of this issue?

This issue can be somewhat inconsistent as a build will succeed if a build has already run without running deno clean