I've opened lot of boxes in The end of the Time and receive hi-level items. If equip sword 172-278 damage for 13 str then it make less damage then normal sword 54-90, char level is 7. Also lot of misses on target.
Did you HAVE 13STR?
There was a bug in the last version (which probably isn't fixed reading your report) that allows you to equip items you didn't have stats for. The stats ARE given, just not listed. AP thinks you attack hand to hand (and you use the animation) but having less than the sword needs leads to constant missed due to lack of AP.
All in all, exactly the story seems to tell, making me believe you equipped it without requirements and see the same...