There has never been a quota. What there has been is if a DPE's pass rate is abnormally high, they just get more surveillance to be sure that it's because the students are prepared and the test is fair, rather than the DPE giving out free tickets or not even doing the test (has happened). Same thing if it's abnormally low, it requires more surveillance. There is a program now where the FSDO calls back many DPE applicants after their test to assess the test and also ensure it was fair. Whether DPEs took this all to mean that they should "fail" a certain number of students to avoid having to have an inspector go on a few more rides with them I don't know, but it seems that is the likely explanation.

As you are progressing through pilot ratings you are getting more used to checkrides and more than any other one, the CFI checkride is about knowing the standards and what is pass/fail. If you get failed for something that is not safety of flight, grossly outside of standards or failure to correct, you should stand up for yourself and speak to the FSDO DPE manager (who is just a regular inspector, nothing special). And if that doesn't work you start going up the management chain. This is very important as you are growing your pilot career and will ultimately have more responsibility and more things at stake. Your pilot in command authority comes from this and if you know you are right, you need to stand up. I give checkrides and I would never want someone being less than fair to me, so that's how I give a checkride and if I make an error, I welcome someone pointing it out. You get a lot more respect admitting to errors than trying to hide them. If a fail is legitimate, then you use it as a learning experience.