How many times can you invade/be invaded? Are the chances lesser after the first one? I have noticed that most of the times there is an invasion at about 30%. After the invasion is over you don't get any other invasion whilst completing the dungeon.
Not sure if the condition "or receiving damage" is true. If you attack you are not receiving damage but you are still in combat. I think it's correct as JETracktor said, just the confition about attacking.