This is a terrible bug/feature

My personal experience with Password Recovery was "interesting".  After entering a password incorrectly three times in a row, the page came up.  I entered the router serial number (which demonstrated that I had physical access to the router) and was not able to get past the security questions.  What appears to have happened was that during the initial configuration, I had skipped over the step of deliberately enabling the Drop Down Menu and selecting each security question, and entering the answer.  Since I had not done that step, none of the questions had been selected and no answers were recorded.

After much swearing, I did a Factory Reset and reconfiguration.  This time, I was very careful to go through the process.  Click the arrow. Pick a question.  Enter the first answer.  Click again.  Enter again.  Once the router was configured, I went back and deliberately entered the password incorrectly three times.  Password Recovery appeared, I entered the serial number and the correct answers, and 'voila', it worked!

This is an easy hypothesis to test.  Do the Factory Reset. Perform the configuration.  But, do not "drop down" and select questions.  Then see how Password Recovery works.