Catacombs: Chain Shot Modifier and misses
While this is slightly ambiguous, the "consecutively" refers to shots taken in the sequence. If you hit A on shot 1 in a sequence, you won't be able to damage A on shot 2 no matter what, but shot 3 is fine.

If I hit A on my first shot, then on my second shot hit B then A, A would still only take the one damage (despite the "change of target").

This limit isn't to force you to change targets but to encourage it, and to limit the damage a sequence can do to a single target. This way the Overseer can't take a boss sequence and just eliminate a single player trivially, and the Barbarian can't use items to take down the boss in two turns.