There is indeed a square visible on the original pictures, but it is transparent, most likely an artifact of JPEG compression.

I recommend using lossless compression in future to prevent these oddities, it may take longer to transmit but so be it.

This so called UFO expert simply filled in the jpeg or video compression artifact by making this transparent square black.

There are many squarish squares visible in pictures like this.

This one is particularly large which makes it slightly suspicious but could be a fluke of luck/chance on having compression artifacts near each other.

Thus for now I call "bull" on this ! LOL.

He just trying to hard, unless you believe in reflective or transparent UFOs !

Bye,
Skybuck.