A safety feature for a spindle swivel has a cylindrical portion that fits inside a spindle receiver. The spindle swivel and spindle receiver have a wavy interface between them that ensures at least one preferred azimuthal orientation between them when they are forced together. A twist lock collar is pivotally attached to the spindle receiver, and may be rotated by a user around a central axis, against the action of a torsion spring, from a locked position to an unlocked position. In the locked position, various ramps inside the twist lock collar force respective steel balls radially inward through respective holes in the spindle receiver to engage respective notches in the cylindrical portion of the spindle swivel. In the unlocked position, the ramps decrease the radial inward force on the steel balls, disengaging them from the notches, and the spindle swivel may be separated from the spindle receiver by the user. The safety feature unlocks only some of the balls from their recesses. The remaining balls are forced thru a channel which prevents direct removal of the spindle without rotation thereof, preventing accidental unexpected disengagement.