Needs a new set of window hinges ( friction stays ) , quite common fro them to go wrong. You may be able to ' jiggle' the window as you close it t get a good seal but the problem won't go away
Are you sure you're not locking into the "ventilation position"?
If you look at the catch, there should be 2 slots and when fully locked, the mushroom bolt on the window should lock into the internal slot.
Debris can prevent locking in this position, so if that's the problem, give it a good clean and try again.
I'm happy to be proved wrong but this has all the hallmarks of someone creating an account (either for genuine reasons or otherwise) then not replying any further. The OP suggests windows (plural) so they've all failed? Also, as pointed out, unless there's a problem we can't make out from the pics, it doesn't look as though an attempt's been made to fully close the window.
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