I am running 2012R2 and have 5 OS image, 2 for Win7, 2 for Win 8.1 and one for a specific tablet. I can do a scheduled update injection on 4 of them without issue, the 64 bit Windows 8.1 Enterprise one is not even giving me the option to schedule updates, it is greyed out. The only thing I can see that is different is that the image has Invariant Language (invariant country) listed next to the language on the summary. The rest have English (united states). I captured these the same way so I am not sure where that is coming from. I have done searches for the issue and I am finding nothing, the only partially relevant result is on this forum with a boot image and VMWare.
I should mention that I built the image using HyperV and captured it using DISM, but I did the exact same thing with the 32 bit version of Win8.1 Enterprise and it is fine. The image does apply perfectly fine if I deploy it.