Black shoe for track of casement window

A quick learner from Seattle says:
Hi there, I am having trouble assessing my next steps as I attempt to repair my casement window. The mechanism to the right is the original and was "slipping" as I attempted to close it. So I ordered the single arm to the right. However I can figure out how to either find a replacement or remove the original and re-install the black shoe for the window track. It says "Truth" and "29" on one side and USA on the other. Any guidance is much appreciated. Thank you.
Thumbnail of the uploaded file named 73555A24-A49E-4B4B-82E6-0ABCCE824CD1.jpeg
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Emily from SWISCO responded:

Hi there!

I see that you ordered our 39-450 operator. This operator is designed to work with the 39-529 track slider and 39-528 track, not the original black slider in your pictures. Look these over and see what you think. 

Anatomy of a casement window
Anatomy of a casement window
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