Hello,
Assuming you're working on an awning window, there are quite a few things that could prevent the window from closing. I'd recommend starting by checking for debris that may be clogging the track or operator linkage. If those areas are clear, check to see if any of the hardware is damaged or corroded. If something stands out to you, we'll need to see a clear photo of the part in question.
The nylon part you mentioned maybe a torque bar bearing, but we'd need to see it removed to know for sure. Take a look at our selection of awning window parts here. Thank you!
