Parts info

Hello,

We can't be sure without being there to troubleshoot the problem but I did notice that there doesn't seem to be a hinge under the operator arms, which should be there to support the weight of the sash. If one of the hinges is missing, that could certainly be contributing to the problem. If you could show us photos of the top hinge that connects the sash to the frame, that would help us narrow down your options. Thank you! 

I do see that the bottom hinge is missing but there must be a hinge at the top of the window sash. Otherwise, the sash would have fallen out of the frame. We'll need to see photos of the top hinge to determine if we carry suitable replacements for the top and bottom. 

Thank you for your patience as we looked into this for you. It's tough to be sure but it seems like the sash may be sagging, which may explain why you hear a loud "pop" when opening the window. The sash is probably rubbing or binding on the frame. If so, you may want to raise the lock keeper up slightly to compensate for the sag, allowing it to engage with the lock properly. I would also recommend removing any excess paint around the window, which could be contributing to the window binding. 

The "pop" may also be caused by the operator missing a few teeth in the gear, which I have seen before. I'd start by cleaning up the frame and hardware, lubricating the hinges and operator, and any other moving parts. If you need a new operator, consider the 39-366 or 39-458 depending on how the specifications compare to yours, along with the 39-520 track.