I've just rented out my house to some tenants and they reported that one of the window hindges is broken. It's actually on two windows like, they just haven't noticed the other one yet

Basically, it's the plastic guide railing thing that is broken - i.e. snapped in half, which makes the window sticky to close. I know nothing about windows, but my dad says I should just superglue the plastic bit together. Trouble is, it's a bit of a bodge job and I want it done properly, but he says it may require a new window altogether. Erm, no... I've checked with insurance and it's not covered. Boo....
Anyone have experience with this? I've attached an illustration below but I only have 1 arm thing attached to the plastic guider, not 2.
