Hi @Tom_Duerr welcome to the community!
Are you seeing the same message InterruptedAtShutdown during the upgrade process from the client side, and only during the upgrade and not during any other time?
If yes, the message InterruptedAtShutdown just means that the driver/client is in the middle of an operation, and it’s being stopped by the server since the server is shutting down. Most newer drivers implements retryable writes and retryable reads to make this situation smoother, but the error can still happen when the operation in question are not retryable (see the linked page for more details about this).
I don’t believe this is an issue per se since 1) the server is shutting down, and 2) the operation got killed because the server needs to shut down. However if you see this error when the server is not shutting down, then this may be unexpected and may need further investigation.
Best regards
Kevin