bulk acknowledge acknowledges events multiple times

have a trigger that has at least one unacknowledged problem state event. go to monitoring -> triggers, acknowledge this event.
make the trigger fire another problem event. this time acknowledge it with bulk acknowledge link from the trigger, then check previous event. it had bulk acknowledge added as well.

all past events (including ok and unknown events) have been acknowledged one more time.

instead bulk acknowledge should operate only on previously unacknowledged problem events