Microsoft DaRT / MDT ISOs not recognized as bootable on 1.4.9?

I’m having issues with “burning” a Microsoft DaRT ISO to USB - our official process uses Rufus but we’re getting weird interactions where Rufus believes a drive is write protected even in situations where it is not so I turned to Etcher to try to resolve. However, Etcher advises the ISO is not a bootable image. It provides the same error for my Microsoft Deployment Toolkit boot ISO. Has anyone run into this issue when using DaRT/MDT and if so how were you able to resolve? I tried using “continue” to flash anyway but the device was not bootable at the end of the process, and in fact was reported by Windows as not containing a valid file system (leading to a request from Windows to format the drive).