Currently, command execution allows only a single subscription from a Flux/Mono:
Template API calls assemble publishers that pre-allocate connections and operate on that particular connection. Once the first subscription terminates, the collection is returned and no longer usable for subsequent subscriptions.
Publishers without a subscription stay with the allocated connection which causes a resource leak because the associated connection is never released.
On a different note: Connections are allocated through a synchronous API which may incur blocking.