Why do items suddenly popup double in the spreadsheet vieuw?

If I add some info, f.i. location to an item that is already in the spreadsheet vieuw, then suddenly it appears double and the copy is numbered with the following number. The total number of items increases by one unit, every time this happens…
What do I do wrong ?

Sorry you are having problems with Spreadsheet View.

Just to clarify, when you are adding something in Spreadsheet View, like a location, then it is the entire item in the Spreadsheet that gets copied?
Does this happen when you add any information to the item ?(eg. Start Date, Notes etc.)
Or is it only specific properties or relationships?