Latest trunk, it only produces corrupted or black dng in any mode (single, best pics, ...) in either manual mode or focus stacking.
Ouch. I hope MLV didn't break most other stuff...
Official nightly version work, so it's obviously something with my setup - I even used the default compiler options from Makefile.user.default ... so it's either the arm compiler (I use the newest version) or some quirk with cygwin. I'll let you know and close this bug when I've found the exact cause.