Unit Tests return 409 conflict intermittently

After a successful build, I tried to run all unit tests (non-parallel). After 21 successful tests, the majority of tests fail on TestInitialize() with a 409 conflict or TestCleanup() with a null reference error.

A failed test can be made to complete successfully if run in Debug mode stepping through code (allowing for a second or so pause between steps) but Run mode may or may not complete with a 409 conflict on either TestInitialize() or TestCleanup().

Is anyone else experiences this behavior? I am using storage in Azure (re., not using local storage).