>>>Did you set it to float? Also add just one field above it with print when condition.
>>>
>>>Also does your detail band have constant band height? It should not be checked.
>>
>>OK I have just one other fields with print when - float is now set
>>
>>How do I set / unset constant band height?
>
>Double click on the detail band, it should give you this dialog.

OK - it's not checked