Try to say in AF Interpret footage advanced tab, that your incoming footage is Rec709
and do not use project settings or keep it in default sRGB. You have to create new adjustment layer
with Effects/Color Correction/Level and clip black at 13 and white at 253 level in 8bit project
if your footage has to be EBU compliant.
So, AF will do the conversion from Rec709 to sRGB and
you can export from RGB to Quictime yuv from there.