"it should not harm if you wire it correctly.
I had same problem when i powered my FC  from the ESC BEC and the capacitor stabilized the voltage from 0,6V oscilations to 0,25V."

"Do you power your flight controller with the ESC BEC? If yes then a band aid would be to solder a 470uF capacitor on a servo wire and connect it to a free pin on the FC so it can fix a bit of those spikes of power brown outs.

But a fix would be to…"