There are numerous problems with this issue. Some elements cannot be loaded into a project, they have to be copy-pasted from another project, such a Detail Group consisting of Detail Lines.
When I copy-paste a Detail Group, this happens:
Revit will over-write some project elements, even though they not related to anything in the Detail Group being pasted:
Yet Revit will dupe Families that, again, have nothing to do with the Detail Group being pasted:
Railings is another element that causes me problems dupes, as railings are made up of multiple components, and Revit make dupes of these components.
The frustrations are further compounded when the dupes are attempted to be deleted. Revit will throw up warnings that the families are used in other types. It instructs to select all in project, and then select a replacement. THIS DOES NOT WORK!!! I've made separate post about it. Furthermore, when investigating the railing types to find the offending dupe families, those dupe families are not even in the railing type!!!
This issue is such a vicious circle of incoherence. This type of nonsensical behavior should be intolerable!