Yaw problem with dodeca hexacopter

last year I build a coaxial hexacopter (so hexa with 12 engines) in a Y6B setup. It did fly well a couple of times before it went into the closet again, and never had the chance to do auto-tuning, etc. Last weekend I had finally some time after a long winter (and spring…) of no flying activity at all, and updated/re-calibrated everything (as I always do when I did not use one of my copters for a while). When taking off, he immidiately starts rotating with no effect of giving counter yaw tru transmitter whatsoever… tried 3 or 4 times with every time the same problem. and landing a spinning 5kg hexa has of course some impact on the landing gear… Flying with a pixhawk 1 and standard parameters…
Very curious to know what the problem is?
link with log: https://drive.google.com/open?id=0B9pK8ZCnKgklVUdzb1k3TzI4QVU