Make sure that:
File > File Options > Text Tab > "Use Roman language line-breaking" is checked.
I know it's not ideal, but maybe try using merge text to see if that will work instead of fields. Also try adding a new field to replace one of the converted ones to see if that solves the breaking issue.
Sounds like something got mixed up in the conversion. I know this isn't a problem in some of the FM12 files I've scratch built.