I've seen this too for repeated high level weapons (2-4 in a row) (swords & bows) that let me kick the AIs butt so I didn't complain.  I had though initially it was just coincidence but now not so sure as I've seen more variety in subsequent games.  I've also seen crap come from these many sequential times but without seeing how the random item results work can't say if it is a bug or not.  I also found it odd that I take out a group of archers and find an axe or sword in the after battle screen.  Shouldn't the combat loot pertain to the unit(s) killed?