You currently support only six rectangular Datamaxtrix formats. DMRE are the same as normal Datamatrix barcodes, DMRE just describes some more rectangular formats. DMRE enables printing barcodes for smaller devices, like medical devices. Because of EU2017/745 regulations all medical devices have to have a unique device idenitifer (UDI).

Further Information:
https://e-d-c.info/projekte/dmre.html

The barcode cannot be read with the property set to false.

Workraound:
Telerik.WinControls.UI.Barcode.Symbology.EAN128 code39Extended1 = new Telerik.WinControls.UI.Barcode.Symbology.EAN128();
code39Extended1.Checksum = true;