I am seeing thousands of these errors since last night. I am running a stress test to see how many concurrent VM's I can provision at a time before the system falls over 
I think I broke something. I have no VM's provisioning, but am still seeing these come through. The error is below.
dcdc1d24-015e-4c8a-a717-c7fb85acdba0: Unexpected exception while executing activity callExternalWorkflowActivityPostDisposing Object reference not set to an instance of an object.
Thank you
-Stephen