I have 4 cache services, two street maps and two aerials, and today I'm noticing white lines on all 4 cache services that is laid out in a grid pattern. I did just re-create tiles on my street cache and finished that yesterday. However, I didn't notice the white lines when I checked service when I finished the first 5 scales a couple days ago. In addition, I haven't touched the two aerial cache in a few years. So that shouldn't have been modified in anyway. Here is a link to a live site that is running all 3 Land Use GIS Website .
I'm running ArcGIS Server 10.3.1 and Portal 10.3.1.