Duplication of profile_values records

I've read of some similar issues about this, but don't see a good solution. In my case, I have 20 profile fields. When I import from a csv file, 3 out of the 20 fields have duplicate records for every user in the profile_values table (name, telephone, and "member since"). The duplicates have values for uid and fid, but nothing for value. The other 17 fields are fine. I can run a query to remove the dups, but would like to get to the root of the problem. Any suggestions?