Casement window plastic hinge cracked

Hi all

The casement window I have doesn’t close completely on the lower hinge leaving a 1 cm gap between the seal. I called a reputable company in SE London to fix it and they said I’m looking at £145 to fix any mechanical issues. I think normally when closing, two plastic hinge butts connect and levers to seal the window. The upper corner closes ok. It seems to be a plastic piece that’s split in the image attached. Seems like bad design as the same spot is thinner than the other areas on that side but it is where it meets the receiving plastic part on the frame. Is this the problem? Is it a simple part that can be sourced and swapped?

Standard window hinge ( friction stay in the industry ). It's quite common to have this issue of not closing on the hinge side on older hinges...just wear and tear. Fairly easy job if you know what you are doing lol

I did t understand. The whole friction stay units have to be changed out and I have to change both top and bottom ones or can I find the plastic part that’s broken and replace it?

It will need to be a replacement pair of hinges ( friction stays)

Thank you. I’ve ordered a new pair of 16” friction stays. Seems a waste of metal though.