Lines drawn on a 2D Canvas have strange "squashing" behaviour

[tiggerbiggo]

Minecraft 1.20.1
Fabric Loader version 0.15.10
Plethora 1.20.1-1.11.7

Example code is below, for a neural interface with overlay glasses

local neural = peripheral.wrap("back")
local canvas = neural.canvas()
canvas.clear()
local w, h = canvas.getSize()
local pointer = canvas.addLine({x=w/2, y=h/2}, {x=w/2, y=h/2}, 0xFFFFFFFF, 5)

local angleDeg = 0
local pointerLength = 10

while true do
    angleDeg = angleDeg + 5

    local pointerX = math.sin(math.rad(angleDeg)) * pointerLength
    local pointerY = math.cos(math.rad(angleDeg)) * pointerLength

    pointer.setPoint(1, pointerX + w/2, pointerY + h/2)
    pointer.setPoint(2, w/2, h/2)
    sleep(0.05)
end

This results in a line that rotates around the center of the screen, but when it goes horizontal the line get so thin it disappears.

[tiggerbiggo]

I cannot get the code to show up consistently. Here's a gist instead if you need it:

https://gist.github.com/tiggerbiggo/ffde0cee7e65f3627125e0d6b03a6c78