As per the documentation of NserviceBus, the default time to wait before triggering the Circuit Breaker is two minutes for SQl Server transport:
Connection Settings • SQL Server Transport • Particular Docs
However, as per my logs, it seems to wait for only 30 seconds in the armed state before initiating a Shutdown.
I tried to look at your GIT repos and the default time to wait is indeed 30s which is in-line with my logs.
NServiceBus.SqlServer/src/NServiceBus.Transport.SqlServer/SqlServerTransport.cs at master · Particular/NServiceBus.SqlServer · GitHub
Can you confirm which should be the default?