Walls and Ceilings - rippled basement ceiling

I've recently noticed the textured ceiling in my basement getting a subtle rippled look to it; also, noticeable dark lines every now and then in a large rectangular shape. Does anybody know what this means?

Hello jwalk and welcome to the forums! ;)

noticeable dark lines every now and then in a large rectangular shape
This sort of sounds like you may have some joint photography issue in this area, usually it would show up over the entire area, but may be only noticeable in certain areas that have the right light conditions.

The rippled effect could be an indication of a moisture problem or poor bonding, probably due to lack of a good primer coat being applied before the texture. Have you ever tried touching the affected area to see if the texture is starting to come loose from the ceiling? Give it a try and post back if you can see any give when you press lightly on it.

I touched the ceiling and the texture does not come off, and there is no give.