my kitchenaid k400 blender handle feels loose, is it supposed to wiggle like that?

No, the jar handle shouldn't feel loose. It's likely because the jar isn't sitting correctly on the base.

1. Unplug the blender.
2. Lift the jar straight off the base.
3. Look at the jar pad on the base. You'll see a slot.
4. Place the jar back on, carefully aligning it with that slot. The jar handle needs to be facing directly towards the control dial.
5. You should feel it settle into place without wobble.

If that didn't work, you might have been carrying the blender by the jar handle, which can disengage the base from the jar over time. Always support and lift the blender from the base itself.

Heads up: A properly seated jar is crucial for operation. If it's not aligned, the blender may not start.