If you have problems burning optical media with the built-in Macrium Reflect optical media burning engine then you can easily create a standard ISO format image file that can be used with any DVD/CD burning software to create your rescue media,
Select the Other Tasks menu and then select Create Rescue Media. 
The Macrium Rescue Media Builder dialog will open:
Select ISO File then enter the file name and click Build.
You can then use most DVD burning software, such as the free ImgBurn to create your physical media.
See also: Creating rescue media