brouken: I have the same problem with my Luca when I first got it. I thought I got myself a lemon, until I noticed that the ratchet inside the wings are not aligned properly that the teeth of the cog is not 'biting' into the groove.
So what I did was (kinda stupid and brave at that time) was pull the wing upwards, stressing it until i heard a click. The reason why I did this is because I had the same problem with one of my SOC's and I did the same thing to force the teeth of the cog to snap it in place of the groove.
But that fixed my Luca and he has been in good shape ever since. Now, I would not recommend anyone to do that as you will have to bear your own responsibility for the damage to your Valk, but I am sharing my experience here, so for thos who dare, give it a shot, but don't way I did not warn you ppl.