Fabric.js: dashed line with clipping looks different on large canvas size - fabricjs

Question

I use a clipping area with fabric.js to create a graph. However, the grid lines look different on a canvas size bigger than about 1000px. It only occurs with imageSmoothingEnabled: false. See the image. Note: the size of the frames have nothing to do with the size of the canvas.
To create the grid lines, I create one original that is wider than the area, and then clone them. The cloned lines are added to the clipArea object. Here is the relevant code.
HTML:
<canvas id="canvas" width="966" height="520"></canvas>
Javascript:
var canvas = new fabric.StaticCanvas('canvas', {
imageSmoothingEnabled: false
});
var rect = new fabric.Rect({
originX: 'left',
originY: 'top',
fill: 'transparent',
width: x1-x0,
height: y1-y0
});
var clipArea = new fabric.Group([rect], {
originX: 'left',
originY: 'top',
width: canvas.width*2,
height: canvas.height*2,
left: -canvas.width,
top: -canvas.height
});
rect=clipArea.item(0)
rect.set({left: x0,top: y0});
clipArea.clipPath = rect;
canvas.add(clipArea);
var yline = new fabric.Line([0, 0, 1200, 0], {
originX: 'left',
originY: 'center',
stroke: myFrameColor,
strokeWidth: 2,
strokeDashArray: [1, 3.4]
});
// clipArea.add(yline)
Of course I could draw the gridlines in a different way without using clipping, but I need a clipping area anyway. And I'd like to understand why this is happening.