In electricflower/postprocess.js, the code is trying to create a quarter-width, quarter-height frame buffer, but it actually creates one that's quarter-width and full height.

This is the line:

var qw_qh_fb = tdl.framebuffers.createFramebuffer(w / 4, h, true)

And it should be:

var qw_qh_fb = tdl.framebuffers.createFramebuffer(w / 4, h / 4, true)

Not using quarter-height results in wasted memory and a bit of noticeable ringing in the output (appears as horizontal stripes).