A sill is the lower exterior part of a window frame; the interior trim in the photo is a "stool". Calling it a sill suggests its part of the window frame which it is not.

The only thing I can think of is excessive humidity inside the house but there's no frost on the glass.

Is the stool made of wood? Where is the project located? It may be necessary to remove the stool to see what's below it.

Here is a section detail:

What I notice aboout the detail is the sill doesn't project much and there is no drip at the nose which is why I add a sub-sill to this type of window.

I suppose the seal under where the hardware is attached to the frame at the crank is missing or damaged.

It's the builder's job to contact Andersen. When there's a recall on your car, you don't drive it back to the Ford plant. Same thing here. This could be, and most likely is, installer error.

Avoid shifting the contractor's responsibility to deliver a house that doesn't leak to you, unless you bought the windows and/or installed them.

Usu builder responsibility IF builder purchased windows.

Looks like it could be related to casement window crank. Make sure the window lock is also used as these windows may not seal with locking.

We have not seen moisture intrusion in our Anderson 100 installs but mostly single hung. If its a factory flaw Anderson will likely already know about it.

What climate is this home in?