I have been having a heck of a time over the past three months trying to find out why every time I use EP with a certain client site, it creates duplicate records of many items. I finally cracked the problem and would like to warn other EP users.
The problem is not actually with EP, rather the spreadsheet program (specifically Excel in this case, but likely applicable to other packages). For some unexplained reason, Excel strips the leading zeroes off of the model number, and will not return them when you set the field to text. Then when you save, it saves the new number (missing the leading zeroes) as the model, and EP interprets this as a new product (and of course you restore from a backup because the database is all screwed up now, and never realize why EP is doing this).
So my recommendation is to make sure you do not use leading zeroes in a model number, or ensure that you use one non-numeric character in the model number (a text character gets around the dropping leading zeroes).
Now the fun part is manually replacing all the ISBN numbers in the model number field with something else, to remove to ones with leading zeroes. ARGH! :angry: