I just finished testing the Beta 4 with a, not so old, windows 10 enterprise insider preview (build 14393.0) which was released in the end of july 2016. But this is not the LTSB iso.
I tried this iso with your wccf ... and it seems to work with beta 4. I do not have experienced the reboot loop.
Could you please try with Beta 4, which will be released later today, thanks.