I believe shapers have a reputation for "walking" around the workshop unless secured somehow.
There was a story a while back about an amateur machinist getting his hands on a nice big old shaper, spending weeks stripping down, cleaning and refurbishing it, getting it installed and set up and excitedly switching it on, whereupon it proceeded to lazily march backwards through the wall of the workshop, collapsing the roof and so on.
Fact or myth, my take-home from this story was that a shaper stand (like any other machine stand) should ideally be strong, massive, rigid and firmly attached to something structural…
On a slight tangent, I was recently talking to my other half's grandfather who was an Engineer at BA his whole career. I felt a little queasy when he told me how as a teenager, he and the other apprentices would sit atop the ram of the big shaper and see how long they could hold on, rather like those "bucking bronco" rides at the fair. Surprisingly, he's still got all his limbs.
Adam