Block and channel replacement

Question

Some plastic parts broke on what I believe to be a block and tackle channel balance. I have a single hung vinyl window. I attempted to remove the balance, but the foot isn't like any other I found online - no U or C foot to turn with a screwdriver. The blue piece pictured is locked in the channel, no way to get it out. What is this part called and how do I remove it, so I can order a replacement?

User submitted photos of window hardware.

Tom · Accepted Answer

I'd have to see it out of the window before I can identify it. Many important details are obscured. See the video below for instructions on how you can remove it.