CSS seems not to load correctly

System Information
  • Strapi Version: 3.6.8
  • Operating System: macOS BigSur 11.6
  • Database: -
  • Node Version: 14.5.4
  • NPM Version: 7.20.6
  • Yarn Version: 1.22.10

I’m using Strapi for several projects. Until today everything worked fine but suddenly it seems that for one project the css is not loading correctly. E.g. on the login screen, the language dropdown is not rendered correctly:

I compared with other working strapi projects and the only difference I could see is that in this project here not all css styles are loaded when taking a look the UI elements using the browser’s inspector (even though no error etc. is logged to the console). I cleared the build, .cache and node_modules folder with no effect.
Do you guys have any idea where this is coming from?

EDIT: This is both for development and production environment and on my local machine (mac) as well as on a linux server (ubuntu 18.04.2)

Solved it! Problem was that I set up a yarn workspace with 2 packages: A nuxtjs frontend and the strapi backend. Instead of executing the yarn workspace commands I only executed them inside the strapi folder which consequently didn’t have all needed packages due to the workspace setup.