I have wanted to ask about this for the last two years but figured "hey they all gotta do it" my SP-300V does a side to side shimmy, I was concerned that mine might not have a stable enough foundation, my printer sits on a 5' x 10' sheet of MDO which sits on carpet but I believe it's just caused by the force of the head stopping at the end of each pass, just kind of odd to watch it but mine has always done this, never thought to ask the tech about it.