Aluminium window handle spins but won't lock — is the multipoint mechanism gone, and can it be repaired?

Good news first: a spinning or stiff handle is almost always a hardware problem, not a dead window — so don't let anyone talk you into full replacements over this.

What you've got is a multipoint lock (the espagnolette). The handle turns a little gearbox in the edge of the window, which slides steel rods up and down; cams on those rods hook into keeps on the frame and pull the leaf tight at several points at once.

• Handle spins, nothing locks = the gearbox teeth have stripped. It's usually the end of a long story — the mechanism went stiff, everyone forced it, and the gears eventually gave up. The gearbox is a replaceable part.
• Handle stiff = either the cams are dry with dust and heat (they want cleaning and a little grease, not runny oil), or the leaf has dropped slightly on its hinges so the cams are fighting the keeps. That's the early version of the same problem — sort it now and you save the gearbox.

All of it — gearbox, rods, keeps — is replaceable hardware matched to your window's profile (the section shape) and the original system; the mechanism standards come from makers like Roto. The fix is to identify the profile, fit the right gearbox, and realign the keeps if the leaf has sagged. For matching and fitting that's a job for an aluminium and metalwork specialist in Dubai rather than a generic handle off a shelf — the wrong gearbox either won't line up or strips again in a season.

While they're there, get them to service the other windows too (clean and grease the cams, check the keeps) — that's what stops the stiff ones turning into spinning ones. If any of your doors are also sticking, that's a slightly different job — worth reading this thread.