Fold line is fast, but garbage. Don't use it.
Posts made by Chris Kenney
RE: Gaps in engraving when using FoldLine
I speak from limited experience, but I have experienced the same thing, and no longer use fold line at all.
While it is faster, the gaps are unacceptable to me.
Try real point - line by line, scan, or point, 10 - 15 lines per mm. That will give better results.