I need to update this thread since actually the version reached is 1.5.8
But anyway: an italian user who emailed me found the most crazy bug. In short, if you used Protect or Disrupt in a fight during SOME specific scenes, like Michelle personal quest, it would mark it finished internally but still leaving the quest unfinished (so missing the XP).
Is probably the most rare bug ever found
is triggered only if you use those two skills during the fight, otherwise never happens (this is also due to my bad coding using arrays instead of classes, but let's not go too much into details!
Right now I'm fixing the Steam version only but once I've finished with it will also update the version on my site of course.