To answer this question, consider the following:
Items in service:
position is defined by their current "Installation" functional location
position is defined by their current "Installation" functional location
Items in storage:
position is defined by the current storage location
When an item is installed to a functional location (using a WO or edited directly on the equipment properties page), the storage location doesn't change, only the installation position. By not changing the storage location, if you need to return that equipment to stock, you will know where it goes.
You can see the list of items currently installed on a location on the equipment search console by searching the "Installation" functional location (set it to the machine you are looking for.