I've been using Connect Systems products for some time and have a number of codeplugs for many of their handheld and mobile products. Even using N0CSG contact converter, I've had trouble exporting and importing contact info to/from other manufacturers radios. The problem that I seem to see is that the fields used by one radio don't necessarily match those used in another. The only solution I've found that is successful is to:
1. create a blank codeplug for the radio I'm programming
2. export the contacts to an Excel spreadsheet to generate a list of fields
3. Export the contacts from a programmed radio in and Excel spreadsheet
4. Copy/paste the relevant columns of the populated spreadsheet into the blank spreadsheet for the new radio, disregarding any columns that
aren't present in the new radio's spreadsheet.
5. Import the now populated new radio spreadsheet back into the new radio's codeplug.
It's a bit more work but it seems to function well if I pay attention to the details and format of each of the spreadsheets.