split_linestrings raises RuntimeError with specific example

[tomalrussell]

With line:

LINESTRING (415805.57 430046.95, 415800 430015, 415810.18 429959.41, 415814.15 429937.72, 415815.48 429884.19, 415812.89 429871.1)

and grid:

GridDefinition(
    crs=CRS.from_epsg(27700), 
    width=120163, 
    height=259542, 
    transform=(5.0, 0.0, 54675.0, 0.0, -5.0, 1217320.0)
)

snail.core.intersections.split_linestring raises this error:

RuntimeError: Unexpected points while splitting line:
  start(415806,430047)
  end(415800,430015)
  run: -5.57
  rise: -31.95
  pE(-5.57,-31.95) length 32.4319
  pN(-5.57,-31.95) length 32.4319