A squegging or self-blocking oscillator produces an intermittent or changing output signal.
The oscillation stops when the operation point no longer fulfills the Barkhausen stability criterion.
The high-frequency oscillations cause heavy currents in the output stages and, with poor power supply decoupling, these upset the input stage biasing and disrupt the high frequency oscillations.
Squegging in audio amplifiers is commonly called motorboating because it sounds in the loudspeaker like an outboard boat motor at low speed.
A series resistor or a ferrite bead close to the gate or base connector of the active element reduces high frequency oscillations.