3 failures for a single check ride is bad. But it does not necessarily show a failure of just YOU, the applicant for the certificate. Whenever a student fails a check ride (in my opinion) part of that blame falls on the student’s flight instructor.
That being said I too have been on the receiving end of a DPE who seemed out to fail someone. I failed my initial private pilot oral over what was a line of questions I was not prepared to answer. My CFI didn’t know the answers either. And my flight school never used that DPE again. It happens. But you have to own it.
Don’t try to deflect any blame on anyone, including the DPE. Own your mistakes. Use them as a way to show that you were faced with an obstacle and you overcame it and are better for it. And you shouldn’t have any problems getting on with a regional. If you would like to discuss a positive way to handle some tough questions like that in an interview setting, feel free to send me a private message and we can chat.