UPVC handle stiff to open

[Robbox]

Some handles on our windows are very stiff to release. It seems to be mainly on the small toplights in the bathroom and toilet windows.
It feels like the mechanism needs some lube, but not sure how to go about this. The handles need replacing too as they have become loose.

 

[Gazman16]

Start with silicone spray or graphite spray on all moving parts. Give them a good soaking and see how it goes.

 

[Rignall Locksmiths]

It is also worth looking to see if the window is hung properly. If the locking points are scraping on the keeps it may also make it stiff. But definitely worth giving a spray with silicone spray. The handles should just tighten up with the screws.