A minimal working example is given via:
{{{1, 4} -> "A"}, {{2, 2} -> "B"}, {{3, 1} -> "C"}, {{3, 7} -> "D"}, {{4, 5} -> "E"}, {{4, 5} -> "F"}, {{5, 3} -> "G"}, {{6, 6} ->"H"}}ListPlot[%]
As can be seen, "E" and "F" have not been labeled. I am happy about a general solution but also a fix-around for this specific problem would be great.