Funny you brought that up. I was just out taking some pics of the dotted lines on the back of the 1/4" boards. I don’t notice any dots on the 1/8" boards.
I will mention, for those that may not have seen my post about my serrated edges problem (towards end of thread), some areas I am seeing are very similar to those. We concluded (so I thought), after much testing, that there was some sort of bug in LB. It was associated with the kerf settings. I had to zero out the kerf settings to get rid of the serrated edges. That problem was very noticeable on 1/8" boards where I do not seem to notice this issue on the thinner stock (although I have not ran any thinner stock lately). But it is very noticeable on the bottom side of the 1/4" boards. I am beginning to think the serrated edge issue is not really resolved 
While taking my pics, I noticed that the dotted lines are mostly where double sided tape was on the bottom side of the boards. On boards with no tape on the bottom side, the edges are more serrated than dotted. Because most of my recent work has been with the tape on the bottom side I assumed the issue was dotted lines.
Here is the taped side
Here are a couple with no tape
I will say that for the most part the cut edges on the top of the material is pretty clean and crisp.
Thanks