Just upgraded to the beta version (3.4) of the Dependency Injection (DI) package. On running the same test suite, we are getting new circular reference errors that weren't there in version 3.3. The codebase and test suite are exactly the same and only the DI package has been upgraded. Also on digging much deeper, the circular references don't really seem to exist. Just reverted back to the old Symfony DI version (3.3) using composer and everything is running smoothly again.

Please let me know if you need any more information!