I agree: bizarre - if Bright can read your meters via the DCC there's nothing wrong with them.
It must be an issue with EOn which they don't seem willing to admit to.
My journey through Next Drive has been reasonably good, except that
1) EOn can't update the dual tariff onto my meter (for costing information only) so the costs on the IHD are meaningless
2) The EOn app can't display the dual tariff so the usage in that is meaningless too
3) EOn don't seem to be able to bill you consistently for your electricity (the statement I've had was correct, but didn't seem to come automatically, along with the monthly Gas statement)
The only way you can get your true costs is to enter your dual tariff rate/time into Bright, or download the raw ½hr data from Glowmarkt and do your own spreadsheet