flat symbol in chord names

I am guessing you tried placing the flat sign using the F2 palette or otherwise using an actual flat sign. Don't. Use the letter "b", and it automatically turns into a flat sign when you finish chord symbol entry. Ditto for "#" for sharp. And then these turn back into "b" and "#" when you go back to edit the chord symbol. Using the actual flat and sharp signs produces the unwanted effect you are seeing, and it also prevents the chord from being "recognized" properly and hence transposed, exported to MusicXML, etc.