Broke it again! =)
When you scroll down to the bottom of a post the Red Tracker buries itself below the bottom border. Using Google Chrome and a touchscreen laptop with a very non-standard resolution (1366x768), so probably need confirmation here from others if it's not too much trouble.
I could reproduce that on my 1920x1080 desktop only by resizing the chrome window. That is, I scrolled down to just before it disappeared (it doesn't disappear, it gets pushed down below the screen using position:relative and a pixel calculation - maybe using display:none or visibility:hidden instead would fix your bug?), then expanded the window slightly so the main body shifted upward while the red tracker did not. Its position only updates on scroll events, not resize events.
