In case DFDM has a bad, unseen character, go into it, edit the field, and manually type in an N.
If that doesn't work, not that it's a great workaround, but you could you default to ""Year End"" and (assuming it will actually only reset at Year End) when they do their year end processing, part of the process is to change the next Journal and Register numbers manually. If this does work, it would at least give you a little time to figure it out (assuming year end isn't soon) and they'd only need to do it one time a year. Or, they could upgrade...