A bug, there's clearly a maximum amount of packets that can be alive onscreen at once, as evidenced by this following puzzle, which should be solvable in one click, but in fact requires clicking the port more than once to complete.
9G8,8D7,7D8,7D7,5D7,4D8,4D8,5D7,2D7,1D8,1D8,2B6,2B6,1B6,3B6,4B6,5B6,6B6,7B6,8D5,1D4,1D4,2D5,2D4,4D5,4D5,5D4,5D4,7D5,7D4,8B5,8B3,0B3,1B3,3B3,4B3,6B3,7D2,8D2,7D1,7D1,5D1,4D2,4D2,5D1,2D1,1D2,1D2,2B0,0B0,2B0,3B0,5B0,6B0,8B2,3B2,6D5,0D7,0B8,0B4,0B8,3B8,6B7,8B2,0A0,1>65B7,6A0,4>67B7,3A0,7>69B6,0B4,3B4,6A1,8>73B5,3A3,2>75B5,6A3,5>77B3,8P1,-1