I've had it rarely happen when stacking massacre missions and getting incoming enemy alerts. Sometimes the alert doesnt update after each intercepting pirate is killed like it normally does where it tells you who's coming next. Then I just get a stream of interdictions until the mission is completed. It's really rare but never bothers me really saves me the trouble of having to hunt them down since their kills count towards the massacre mission totals.I have to say that is unlucky I have never had that many random interdiction attempts in one run, anyone would think you were taking on and stacking missions with the opposition warning.
For those times I don't fancy meeting lots of pirates I always avoid missions, sorry that's a bit ingenuous I almost always avoid missions unless ranking up or unlocking a permit I don't want to play a game and have someone ordering me about.