It's just natural movement. Added to by any walking around up there

Unfortunately that is exactly what happens when painting inside a surface exposed to the elements.

That is not the paint cracking; it is the wall that is cracking. As others have stated, it is not usual.

Appreciate it. I was concerned that there was a more serious issue at hand. I don’t see any signs of water leakage or anything, just the cracks

Yeah we painted the whole inside of the house, the attic/loft included. I just wanted to make sure there wasn’t a more serious issue at hand like water damage or a leaky roof.

I think you are correct, it may just be the way the wall is. I understand that it may be due to the natural movement of the house from what I have read. Do you think there is another issue at play based on the photos?

I do not see anything else, but there are limitations using photos. It would not hurt to have a handyman or other professional to look at the walls.

The only times I have seen straight cracks like these is when there is wall movement or when drywall tape fails due to moisture. This is an exterior wall so you may have moisture seeping in through your siding or from around that window.

It could be that the framing around that window is slack and the wind load is allowing the wall to flex. What is curious is that the cracks are only beneath the window and only vertical. If there was flex, a structural failing, I would presume to see diagonal cracks from the corners of the window.

You can have someone test for moisture content in the wall. I would call someone who does basement waterproofing. They would have the tool.

If you had wet spots or stains I would be worried, but you should be fine