Window Track hangers

If I can find replacements for these track hangers, does anyone know how to actually replace them? It seems like it would have to be done before the window was framed in. Just need to replace the bottom piece in my hand.

The bottom part is called a shoe. At the top of the balancer channel there are two screws. Undo them and that assembly should slide right out. The shoe is then pushed to the top and slides out of the same spot.

Is it broken in some way? It looks like the metal loop end just needs to get placed into the shoe.

You can search for parts to send a picture to and they will tell you what you need as far as parts.