Always save a copy of your document with the EndNote connection intact.
This will stop any of your citations from being updated by EndNote. This will turn all of your citations in Word into plain-text. From the EndNote Library: If you are in Word, click EndNote X9 tab and click on the Go To EndNote icon: In the EndNote library, click the Insert Citation icon ( ). If you want to break the link between EndNote and Word, you can do that. Type the author (s) name into the Find & Insert My References box and select the relevant reference then click Insert.
Why - EndNote and Word are connected, and EndNote will automatically fix, scan, and update your citations.