syncing/merging

The past few weeks when I've combined multiple fillable forms into adobe (these can be 50-150+ pages long), I will enter a name in one field and it will change it for EVERY single line on other documents deleting the other names/information I had entered.  I work in the legal field so this is VERY difficult since we need complete accuracy.  How can I make this stop?  I haven't changed anything since October and didn't have issues until March.