ESRI products have always struggled with symbol consistency, especially line gaps with markers. I was hoping ArcGIS Pro would eliminate these issues, but it did not. In my Format Line Symbol window the line looks perfect, but on the map it gets screwy. I understand the curves of the line puts the software in a state of confusion, but the legend isn't even correct, it's a straight line!!!!! In addition, the circles change position when I zoom in on the layout. I hope someone has a solution because it's these types of issues that drives map makers like myself nuts.
from the legend: