What is causing this window to open, but not close?
When you try to close it, the cam screw in the unit backs out. That is the drive that will open and close the window. It should not unscrew out. There is some sort of nut or locking device on the end of it to keep it from backing and allowing it to close the window. That locking device is obviously broken. You might be able to disassemble the unit and fix the broken part. I think your best bet is to replace the opening device. Many home stores carry replacements and if you can find a name on it, you can probably get it online. Good luck and stay safe.