@JNarz19
I rebuilt the same lot about a year ago and seem to remember running into something similar but now that was a dozen or so lots ago, so the details are a bit fuzzy on what I actually did. But I think my reno was more extensive that yours judging from the pic. I widened the building as much as I could, so I ended up demolishing the entire thing a bit at the time, more or less, and put in a full 2nd floor and made a usable attic as well as multiple basements and a new floorplan throughout. And to make a usable attic, I deleted the roof and used half gable roofs. I do remember getting the curve right took forever since the roof was 3 pieces instead of the original 1. 😃
Another thing you could try to see is if it caused by the roof or not is to delete the roof and see if goes away or stays. If it goes away, then it's the roof for sure. If not, it's something else.
If you want to, I'm willing to take a look at the lot to see if I can find what's wrong and find a fix if you are willing to upload it to the Gallery. Just reply here with the lot name and your user name on the Gallery, if different than the one you use here (JNarz19). It will be tomorrow before I could take a look at it so no rush.
Hope this helps.