Ok, I tried fooling around with animations a bit.
I wanted to make a flat general march animation (i.e. the SceneRoot bone's z coordinate shouldn't move), so I extracted the animation and skeleton packs, copied the skeleton, imported and edited the animation file (without changing the y and x coordinates of the bone in the key frames).
Then I re-exported the file, repacked it and started the game.
The surprise was that the general moved maybe three times faster than he did before I changed the animation.

Following, I also tried to import and export the original animation, which basically had the same effect, with added wobbling.

So, does anybody have an idea what could cause this or how to work around it?