holy serious RouteView shenanigans batman!
good job on the build, though.

here is the core function that draws the gridlines in RouteView ->
MapView/Forms/Observers/RouteView/RoutePanel.cs
DrawGridLines()
if you want to play with it idk.
note: HalfWidth and HalfHeight are (non-trivially) variables used to translate between cartesian and isometric coordinates ... but offhand i don't have a clue what's going on
EDIT: It might be the PixelOffsetMode on line #138
_graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
ie, try a different mode ... like none or half ...