Program: 55833
Project: 55833
Buggy source:
/** 
 * Draws the main content (buildings, settlers, ...), assuming the context is set up.
 */
private void drawMain(FloatRectangle screen){
  short height=map.getHeight();
  short width=map.getWidth();
  MapRectangle area=this.context.getConverter().getMapForScreen(screen);
  double bottomdrawy=screen.getMinY() - OVERDRAW_BOTTOM_PX;
  boolean linePartuallyVisible=true;
  for (int line=0; line < area.getLines() + 50 && linePartuallyVisible; line++) {
    int y=area.getLineY(line);
    if (y < 0) {
      continue;
    }
    if (y >= height) {
      break;
    }
    linePartuallyVisible=false;
    int endX=Math.min(area.getLineEndX(line),width - 1);
    int startX=Math.max(area.getLineStartX(line),0);
    for (int x=startX; x <= endX; x=map.nextDrawableX(x,y,endX)) {
      drawTile(x,y);
      if (!linePartuallyVisible) {
        double drawspacey=this.context.getConverter().getViewY(x,y,this.context.getHeight(x,y));
        if (drawspacey > bottomdrawy) {
          linePartuallyVisible=true;
        }
      }
    }
  }
  if (placementBuilding != null) {
    ShortPoint2D underMouse=this.context.getPositionOnScreen((float)mousePosition.getX(),(float)mousePosition.getY());
    IMapObject mapObject=context.getMap().getMapObjectsAt(underMouse.x,underMouse.y);
    if (mapObject != null && mapObject.getMapObject(EMapObjectType.CONSTRUCTION_MARK) != null) {
      this.objectDrawer.drawMapObject(underMouse.x,underMouse.y,placementBuilding);
    }
  }
  if (debugColorMode != EDebugColorModes.NONE) {
    drawDebugColors();
  }
  context.getDrawBuffer().flush();
}

Fixed version (ground truth):
/** 
 * Draws the main content (buildings, settlers, ...), assuming the context is set up.
 */
private void drawMain(FloatRectangle screen){
  short height=map.getHeight();
  short width=map.getWidth();
  MapRectangle area=this.context.getConverter().getMapForScreen(screen);
  double bottomdrawy=screen.getMinY() - OVERDRAW_BOTTOM_PX;
  boolean linePartuallyVisible=true;
  for (int line=0; line < area.getLines() + 50 && linePartuallyVisible; line++) {
    int y=area.getLineY(line);
    if (y < 0) {
      continue;
    }
    if (y >= height) {
      break;
    }
    linePartuallyVisible=false;
    int endX=Math.min(area.getLineEndX(line),width - 1);
    int startX=Math.max(area.getLineStartX(line),0);
    for (int x=startX; x <= endX; x=map.nextDrawableX(x,y,endX)) {
      drawTile(x,y);
      if (!linePartuallyVisible) {
        double drawspacey=this.context.getConverter().getViewY(x,y,this.context.getHeight(x,y));
        if (drawspacey > bottomdrawy) {
          linePartuallyVisible=true;
        }
      }
    }
  }
  if (placementBuilding != null) {
    ShortPoint2D underMouse=this.context.getPositionOnScreen((float)mousePosition.getX(),(float)mousePosition.getY());
    if (0 <= underMouse.x && underMouse.x < width && 0 <= underMouse.y && underMouse.y < height) {
      IMapObject mapObject=map.getMapObjectsAt(underMouse.x,underMouse.y);
      if (mapObject != null && mapObject.getMapObject(EMapObjectType.CONSTRUCTION_MARK) != null) {
        this.objectDrawer.drawMapObject(underMouse.x,underMouse.y,placementBuilding);
      }
    }
  }
  if (debugColorMode != EDebugColorModes.NONE) {
    drawDebugColors();
  }
  context.getDrawBuffer().flush();
}