General comment: 5 stages looks like a very small number. Your frequency
will be very high. You may want to increase the nbr of stages;
obviously, it has to be an odd number (3,5,7,...)to oscillate. What is
less known is that it should also be preferably a prime number
(3,5,7,11, ...) to avoid harmonics resonance, which is a form of
instability.

Regards,
Pierre x286