I have a 1833 device, and not the one on your video, and it shows a negative ESR when measured with a 600mV signal, when measured with a 300mV signal, the readings are positive. The capacitor and frequency are the same.
Thanks for the update, but the problem remains, on film capacitors when measured at 600mV, it shows negative ESR, when measuring the same capacitor at 300mV, the result is correct.