2D array works, but then not

I am using the “Microsoft MakeCode for Circuit Playground Express” app on a Windows 10 PC. The following JavaScript works fine – It converts between Blocks and JavaScript. The Console output is as expected. The .uf2 file can be save file to hard drive. No problems.

let array2D = [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
console.logValue("array2DLen", array2D.length)
console.logValue("array2D[0]Len", array2D[0].length)
console.logValue("array2D[1]Len", array2D[1].length)
console.logValue("array2D[2]Len", array2D[2].length)
for (let idx0 = 0; idx0 <= array2D.length - 1; idx0++) {
    for (let idx1 = 0; idx1 <= array2D[idx0].length - 1; idx1++) {
        console.logValue("[][]", array2D[idx0][idx1])
    }
}

But change the array to what I really want to use in my program:
[[16515072, 14164992, 11553792, 8942592, 6331392, 3981312, 1370112, 60432, 50232, 40032, 30852, 20652, 10452, 252, 2359512, 4718772, 7340172, 9961572, 12582972, 14942232], [16711680, 14622720, 12533760, 10444800, 8421376, 6332160, 4243200, 2154240, 65280, 57120, 48960, 40800, 32896, 24735, 16575, 8415, 255, 2097375, 4194495, 6291615, 8388736, 10420320, 12517440, 14614560], [16711680, 16524288, 15880448, 14385920, 11842560, 8641280, 5370368, 2423808, 65280, 64548, 62033, 56195, 46260, 33755, 20978, 9468, 255, 2359548, 5308658, 8585435, 11796660, 14352515, 15859793, 16515108]]

That is an array of 3 arrays with length 20, 24, and 24. It still converts fine between JavaScript and Blocks, and Console output is as expected. (So far so good.) But trying to save it to hard drive results in “Compilation failed, please check your program for errors.

Is this a defect or documented somewhere as expected behavior?
Where is the best place to submit issues like this?

This is definitely a bug! Thanks for reporting. I created an issue for it here:

You can file any other issues you find in that repository