You can try the following:
-Try burning at lower speeds (Highly effective).
-Try using different brands of quality blank media like Taiyo Yuden, or Sony.
-Try upgrading your writer's firmware.
In the meantime lets reinstall again the program and add again the files. You can reinstall the software from the next link:
https://www.nch.com.au/components/burnsetup.exe
If you continue having problems please send the information to the Technical support using this link: https://www.nch.com.au/support/supportcontact.html?software=ExpressBurn