Turn off the Instant Formatting function in Word when working with a large document Give your backup files meaningful names that include, for example, a version number and a date., e.g.enlx file which can be transferred to another computer or backed up on a USB stick or on cloud storage.
Check your import results, especially when working with sources such as Google Scholar that may have inconsistent data. It will make it easier to use a style, but you will still need the manual. EndNote does not replace style manuals.