It doesn’t spike to me either, at least not in the web player:
As you can see, I tried drawing some different shapes and lines, and there was no spikes at all. The line at the very bottom of the project is drawn by hand, so it wasn’t the bug that made the line “spiked”.
That might be the problem, as there have been several bugs related to the rotation of the device.
Yeah, I haven’t experienced the bug before, but maybe @Kikflip made this drawing pad on an iPhone. I might be wrong, but when I play the project in the web player, it seems smaller than projects created with an iPad usually are, so this project might be created on an iPhone.
I haven’t looked in the code, but this project doesn’t lag and you can’t change any colors, so unless there are any code for that, it shouldn’t be the code that is causing the bug.