"ik_back" bone of MHX rig is freefloating

[Jake]

A bone called “ik_back” under the Root collection is parented to the master bone, which means when you pose a model, it remains static in the air. Should have it parented to the hip bone that is also in the Root bone collection.

[Alessandro Padovani]

That is as intended, this is not a bug, indeed the purpose is to keep the shoulders while you pose the hip. If there’s nothing to add please close as invalid.

[Jake]

Yes, but if you move the body to the floor or far away, the ik back remains in the initial position always and it is a bit of an eye sore. I didn’t notice that the model would break in any way after I manually made it a child of the hip bone and then moved the body far away from the rest position.

[Alessandro Padovani]

To pose the whole figure you use the master bone. Then if you don't want the ik spine you can uncheck it in the mhx options.