I don't know how a couple old student busts would effect the computer generated selection for an interview. If I had to venture a guess 3 or more busts or something more recent would probably be a factor. They will ask you about them at the interview and it's your opportunity to own it and be humble. It's an obstacle you overcome and it's your opportunity to check some boxes. This may actually be a positive rather than a negative since it shows you are human. I was a part 61 civilian flight instructor and had some very sharp students bust check rides. Not sure what type of training you had but there was always potential for a failure with a bad roll of the dice.