I'm merging from the duplicate items section. When you save the same paper two or three times on different days, and you cite them separately, it's the same paper but referenced, for example, as 222, 223, and 224 in Word. When you merge, sometimes they become all 222, because it's the same reference, but sometimes Zotero places all the duplicate references in the trash instead of merging them. In word the old references that were linked from a library folder are no longer there (it's in the trash), so it puts another one from the folder library path.