Armature control, same value different position issue !

Hi guys, i did use blender before as well but now fir a first time i am experiencing an issues where an armature bone has same values for position and rotation but its position in viewport is different. Non of the bone parents in the hierarchy is animated… don’t have any constraints as well… it is just a weird pop in position between firs and last frame of a run cycle…

Any chance this to be a known issue or someone run into this as well because i just can not find a reason for this !
I am using Blender 2.78c !

Thank You !