This thing happened at my office. I was working on a long frame range shot and was doing hair and beard roto. There were many shapes in my project file that the file took like a minute to open properly.
Problem is, I used Bezier to make shapes and as I do cardinal in every frames(due to change in hair position and style) the shapes gets invisible in certain frames, only the points can be seen and not the spline(happened for few shapes). And it effected the Alpha Matte. I rendered it from Silhouette, the Alpha mattes and it created horizontal lines and I have to delete the shape for that frame and copy from previous frame to get it corrected. Hard part is to find which shape caused the issue, as there were many shapes and most of them were close to each other.
Note: Pc I use in my office have great specifications as my company does hollywood works. It uses windows 10. And uses intranet connection. Also have latest Silhouette version.