More than three busts is the limit at 9E.

What has been getting guys in trouble is failing to disclose all the failures in the background (incl. oral, flight, 121, 135, etc.).

When the FOIA report comes back (Freedom of Information Act) from the FAA and it doesn't agree with the applicant's story then the individual is let go for failure to disclose.

The moral of the story - disclose all failures in your background on the application, during the pre-interview phone phase, and during the interview itself.