Prior to this the window operated fine?

No, it isn't normal. Are these the wooden, vinyl-clad type, or all vinyl? If they are wood, might there have been a leak that has let the wood swell in that part?

I have difficulty with some of my vinyl replacement windows - due to settling of the house over the years, I think. Some of the upper sashes of the double hungs won't close completely tightly to where I can lock them, and one or two others stick when trying to raise the lower sash.

Definitely odd all of sudden. The 400 series is a vinyl (Permashield) wrapped wood sash and frame window.

Is that real wood shake or a composite material?

It’s hard to tell whether the sash has sagged, or if the frame has bowed upward across the bottom.

Frame on the bottom (not really the supported part of the frame or anything structural) is bowed up.

...

+1, looks like crowning frame more than sagging sash. Hard to tell what may be causing it. As the other pros were alluding to, do you see any issue with the wood on the window in that area... or on the shake siding panel? Is the sash panel actually rubbing in that area?

If the business that replaced them is still in business, ask for them to look at it and ask what could be done to fix it -- and if they stand behind their work.

Have you painted the windows? If so, might be stuck because of the paint. If not, I would run a knife or something very very thin along the sides of the window to see if that would help. Might be "stuck" because of time, heat and/or cold. I would call Anderson and ask them about your problem.

Check the piece around the window on the outside. Can that be removed? Ours can (not sure what our windows are - probably not Andersen 400 but they're double casement), and sometimes with temperature swings that piece pops out a little bit in the middle and catches on the window frame above. Takes a good heave to open it (and a very frightening POP), then I tilt it out, push the offending piece back in, and it's fine. Really annoying though.

That is not removable, it is all wrapped in vinyl (Permashield). I think the guys up above are onto something in that something moved or swelled and is pushing up on the frame.

Thank you, we’re going to take a look at the siding, remove whats under the window. We havent painted the window at all, and it was working until the day before this. I will let you know what we find.

We used ZIP tape to flash around the window and followed the instructions. I might have inprogress pics on my old iPad.