Default values are shown, then overwritten by actual data in many screens
Many screens, like System/NTP Servers/Edit, show default data which is then overwritten by real data. When editing an NTP server, the checkbox values change.
Another example is Storage/Pools. When selected by the user, "No pools" is shown for several seconds, then replaced by the list of pools. This gives the impression that all the pools have vanished.
A short delay while showing nothing or some type of spinner to indicate activity would be much better for the user and more accurate.