angular 9 + ivy ng build --prod fails in CI (github) as incompatible but workslocally on windows + wsl ubuntu with the exact same versions?

Question

So I'm trying to build my angular SPA with ivy and latest version of Angular 9, but the angular material modules are throwing an error in CI when trying to build them. This only happens in the github action and it is right away, console output:

$ ng build --prod --configuration staging


info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

ERROR in node_modules/@angular/material/core/ripple/index.d.ts:11:22 - 
error NG6003: 
Appears in the NgModule.exports of SharedModule, but could not be resolved to an 
NgModule, Component, Directive, or Pipe class.

it fails at the very first step

relevant yaml configuration:

  - name: yarn install, build, and test
              run: |
                  npm install -g @angular/cli
                  ng config -g cli.packageManager yarn
                  yarn config set ignore-engines true
                  yarn install
                  yarn run build:staging
              env:
                  CI: true
                  NODE_AUTH_TOKEN: ${{secrets.PERSONAL_ACCESS_TOKEN}}

Any advice on troubleshooting this/what to try/what I could be missing is appreciated.