Alliance Window
Thanks for reaching out to us! The cam in the pivot shoe has become damaged. This isn't something sold separately, so you'll need to replace the entire shoe.
I believe you'll need the 15-177 Coil Balance Shoe to replace the one here but you'll need to remove it and compare the dimensions below.
The compatible coil is the Series 152 Coil Balance, which is attached to the shoe using the 33-072 screw. Take a look at the video tutorial, tagged below, for detailed instructions on selecting the correct coils spring.
The 15-143 Coil Bushing, 15-144 Coil Bushing Cap, and 15-144 Coil Support Barrel can be used to replace the covers.
Your pivot bar reminds me of the 26-316 Interlocking Pivot Bar. Carefully compare it to your existing hardware to confirm.