It does defy belief that species that are so advanced would manage to have ‘dozens’ of crashes. Either they are prone to making mistakes, despite their advancement, or I think more likely, they’re getting shot down/deactivated in battles with the other alien species. I can’t believe that humans have been able to bring a single one of them down with our tech, whether that tech is publicly known or classified.
The grays are remotely-controlled artificial entities. The telepathic link might not be perfect.
If they actually are being brought down it is from spiritual warfare occurring in the heavenly realms, Ephesians 6:12 κοσμοκράτορας kosmokratoras, cosmic powers and the ἐξουσίας, exousias, authorities.
Satan is attempting illegal acts outside of his given dominion, from out of his authority as ‘Prince of the Power of the Air’. He needs to receive that same authority on the Earth where we are given dominion. He needs US to provide him that open door.
I would doubt there is much to be scraped off the desert rocks though unless left intentionally. What would remain prominent in these encounters however is the lasting psychic after effects from the close-proximity manifestations which do not easily photograph or appear under microscopes.
If what is happening is in fact what I fear, they are the same as shown to us in Daniel Chapter 4, if correct then we are all in great danger.
I believe, like the encounters following us into space and onto the Moon, these are of that class called the Watchers, they operate at the nation state level and act regarding the changing of earthly powers, like when going from a demonic Obama to a President Trump by much prayer and fasting:
“I saw in the visions of my head upon my bed, and, behold, a watcher and an holy one came down from heaven; . .” - Daniel 4:13
“This matter is by the decree of the watchers, and the demand by the word of the holy ones: to the intent that the living may know that the most High ruleth in the kingdom of men, and giveth it to whomsoever he will, and setteth up over it the basest of men.” - Daniel 4:17
The “story” goes, powerful radar beams at Roswell or other bases interfered with their navigation system, causing the crash.