D5000.5 - Turn on Noise / Squeal / Hiss

Hello:

Have a D5000.5 amp I bought new in January 2020. From day 1, the amp has made a noise for a few seconds when powered up, but after the amp gets a signal from the HU, the noise stops.

I have tried:
Removing the RCA inputs, one by one, until all removed - noise still present.
Jumping the remote wire to the power wire, to turn on the amp without anything of the car on - noise is still present.
Disconnecting one by one each speaker output - noise is still present.
The ground wire is 4awg, and right to the frame, at a clean, sanded, ground point. The length is approximately 12 inches.
The power wire is 4awg, and right to the battery positive, with a fuse within 12-inches. The length is approximately 12 feet.

Here are two videos, the first is a normal ignition on (no engine start), and the second, is me jumping the power wire to the remote wire. Both videos the sound starts 6 seconds in.

https://youtu.be/obXWAiVEp3g

https://youtu.be/dUz-FFJmVkA

I believe I am now at the conclusion that this is a faulty amplifier. How else should I test to confirm?