Hey,
I’ve got some experience in both using Unity’s ragdoll wizard and had no problems so far, but I’ve recently created a new character, which has completely new IK rig. It’s really easy to animate it, but:
For some reason my kneeling idle anim doesn’t work like it’s supposed to. Well, images should be the best explanation: first imgsecond img
While creating the rig, I didn’t notice that feet are not children of lowerleg. They’re children of IK objects which are children of root. Works like charm in animating, but doesn’t really seem to work well in ragdoll, since feet are not attached to the leg. here’s how it looks (yellow - foot, red - IK controller).
I don’t see a root bone at the bottom of your biped rig. This suggests that there is no parent that holds your feet controllers and the rest of your model together.
The root bone is the parent bone of all the other bone chains and by default you place it at the bottom of your character model, in the (0,0,0) point of the world space (for a bipedal creature that would be on the “floor” between it’s feet). It serves as a starting point for the whole rig - its pivot and origin.
Once you create that bone, you should have your middle bone, the IK bones for the feet and the knee pole target bones (if you have them) parented to it.
Also, remember that the root bone should never be animated in blender.
Here is an example of a proper hierarchy of bones in a humanoid rig for blender:
