When saving or exporting a Sheet that references a Cached Dynamic View to a new file (DGN or DWG), with Merge Visible Edges enabled, some of the visible edges disappear. I've found that in these cases the Cached Visible Edges accuracy was defined as To Tolerance, and if changed to High instead those missing elements would display.
The reason that the To Tolerance value was producing inconsistent results was due to a value of "1.0000E+1" entered in that field.
When replacing that with an integer value such as 10 or 100 the results were improved. Note that you can use either To Tolerance with an integer value or High instead as long as the results are acceptable.