Just to close out this thread, I think I found a resolution in another thread in the Ultimaker forum here and more specifically in this specific comment. Just wanted to share in case others find my thread in the future!
I have tried cleaning the z-screw and regreasing. Every once in a while the layer issue seems to not happen. But I have a whole table of test prints that show the line through them. I use Cura for my slicing. Is there any chance this could be a software issue? Or do I need to order a new z-screw and motor to fix?