This is a usability issue.

Steps to reproduce:
Go to Monitoring->Maps->select a map->Edit Maps

Select any element and modify its host and then click 'Apply' button -> it looks like nothing happens and button is not clickable

It makes sense that when changing coordinates it is not necessary to show any feedback to the user as he can see the element moving on the map.
However, if user updates the host element it is very unclear that the change indeed was applied.
User then closes the windows thinking that changes were not saved anywhere. (Yes, next he will click the 'Update' button to save the whole map - but that is not obvious that the initial change was registered anywhere in the system.)