It seems that Transform tool is applying more changes than required when skewing elements.
It works fine the first time you Skew an element, but if you skew it again, then it starts to modify other values like Translation, Rotation and Scale.

Besides that, because we initialize the RenderTransformOrigin to 0.5,0.5 if it wasn't set, skewing is adding translation when using the adorner to keep the element in the same position.

This issue is solved already, this ticket should be closed