Designating a new pool master via CLI on the current master fails on 7.0

The command:

xe pool-designate-new-master host-uuid=(UUID-of-slave-server)

when run on the current pool master causes XenCenter to lose connectivity with the pool (as expected), but when reconnected, the original pool master is still the pool master.

If run on a slave server, the operation correctly designates the named host to be the new pool master and XenCenter connects and shows correctly the newly designated host as the new pool master.

Just applied up to XS70E036 in the hope of things improving, and now both hosts have crashed so I cannot continue this research and cannot access them remotely, so will have to manually check them in the server room tomorrow.