The bug is that the game renders the F3 crosshair by render order rather than testing for depth, which ends up causing issues like making the blue line (z-axis) render on top of all other axis lines when you align them at certain angles when it should instead disappear behind them (like if you position yourself with a yaw of 44.3 and a pitch of 1.6, the red line should go above the blue line, but instead the blue line renders above the red line).
Tyler Schuller
The bug is that the game renders the F3 crosshair by render order rather than testing for depth, which ends up causing issues like making the blue line (z-axis) render on top of all other axis lines when you align them at certain angles when it should instead disappear behind them (like if you position yourself with a yaw of 44.3 and a pitch of 1.6, the red line should go above the blue line, but instead the blue line renders above the red line).