When replacing hardware with different hardware model devices, if the same Hostname and addressing information, the Space server will retain the old device's information.

This is expected behavior, in order to have the Space server reflect the new device's information you must delete the old device from NMP and re-discover the devices.

https://www.juniper.net/documentation/us/en/software/junos-space21.3/junos-space-workspaces/topics/concept/junos-space-device-discovery-profile-overview.html