Window flops back to close position

[Jupiter01]

This window used to be nice and stiff when opened. It would hold its position.
Now it drops back unless I still something in to keep it ajar.

I was hoping to see some screws that I can tighten to restore the stiffness it once had but can’t see anything obvious.

Can you please advise. Thanks in advance.

 

[Deleted member 267285]

I’d say at a guess, mechanism goosed.

 

[RandomGrinch]

It looks as if your hinges have a built in opening restrictor.
If you press the 'Press' button (on both sides), and open the window further, do any more fixings become visible?

 

[Jupiter01]

It looks as if your hinges have a built in opening restrictor.
If you press the 'Press' button (on both sides), and open the window further, do any more fixings become visible?

There is a “press” on one side, when I press this, the window open further out. I still didn’t notice any fixings but perhaps I wasn’t looking too carefully when the window was extended. I am keen to look again. Is this where you expect to see some screws that I can adjust?

 

[foxhole]

Sometimes a grub screw in slider on side hinge which can be tighten to reduce movement.

 

[Jupiter01]

Sometimes a grub screw in slider on side hinge which can be tighten to reduce movement.

Definitely couldn’t see one before the “press” button was activated. Need to take a closer look after pressing the “press” option as this extends the opening range

 

[RandomGrinch]

As above, hopefully there is a grub screw in the slider - something like:

I am hoping it becomes visible when the window is opened further!
Otherwise, it is unlike any hinges I have seen.
If it isn't obvious when you open the window further, post another pic