EZ controller is just printing environment. It can't cause any errors. Printer is controlled using D703 system software. All printer parameters are stored inside printer, but not on system software.
The latest D703 system software - version 7. It can be installed on any Windows ( even on W10 x64 PRO ) . On W10 can work EZ controller 6.60 and latter ( the latest 6.80 ) . On D703 also can be in stalled duplex print software ( then on sheet paper can print on both sides ) .
All depends how powerful your computer. On my laptop installed version 6.80 ( running without dongle ) , many system software ( for various printers and scanners ) . I use this computer, when need to test equipment for my customers. Of course on this computer installed many other, but all work well and do not cause any errors.
D703 system software can be installed on two computers ( computer with EZ controller and RIP computer, this way can connect few printers ) , or only on one computer ( with EZ controller - this way can be connected only one printer ) .
I almost sure, that you have hardware problem. Look error number and find troubleshooting on service manual.
I have all - EZ controller, system software, manuals and knowledge how to make D703 service. Last year I installed about 50 of them. They where Fuji DL-430 ( green - white painted D703 ) . Local network of supermarkets ( Morrisons ) quit photo printing business and sold all printers very cheap. The most of them installed using Noritsu software, repaired, so perfectly know problems which can be there. Write private message, if need something.