Unknown error

could anyone please explain to me what this means and how to solve it?

That looks like a problem with Unity, not your code (unless you’re creating Threads or working with disposable objects that haven’t been disposed of). There are three solutions:

  • Restart Unity and pray that it isn’t there when you reopen the project.
  • Reinstall Unity and pray that it’s gone when you reopen the project.
  • Install a newer version of Unity and migrate your project to it, praying that the error doesn’t follow you.