Power Supply Noise
It’s normal for the power supply to emit a high pitched noise when the Silver Bullet is powered off, but the PSU is still plugged into the wall. The PSU likes to see a load. So under normal use when the unit is switched on that noise should diminish. If the unit is intermittently turning off then that points to something else. I have seen an issue once or twice where the 5-pin XLR connector wasn’t making good contact with the pins in the Silver Bullet and this would cause the unit to glitch. Perhaps this is what is happening. There is also a power relay in the unit that turns on the regulators when the power switch is toggled on the back of the unit.