gjalleri, aa that's you. Thanks for the name idea once again.
I just now tried and the integration of those two KBs worked, from both Win10 1803 and same as you 8.1.
Can you please get me the ntlite and ntlite_dism logs at the moment of the error with that latest KB? The skipped one without any popup if I understood correctly.
Before that please unload the image to start fresh, and reboot the machine. Maybe even recopy the clean ISO to be on the safe side, if you haven't done so already.
Btw there is no progression percentage while integrating from Win8.1 as a host and Win10 image, just states "Processing".
Check your temp/scratch directory free space in File - Settings.
Thanks.