Do you think aliens in ufos have visited Earth? (And all things UFO)

Saw an excellent documentary a few years back where a sceptical scientist started looking into contacts with Greys.
He took the most convincing sightings and broke them down to those where the witness had no history of psychosis, alcoholism or drug use and prioritised cases where the witness had more to lose if the story broke (reputation for example).
He investigated about 20 cases where the stories were very hard to refute and came to the conclusion the witnesses were telling the truth about seeing aliens.
As part of his study he gave each witness a comprehensive neurological assessment and discovered all had undiagnosed minor epilepsy.
This causes shapes and colours to distort.
He concluded that all the sightings were actually a sudden onset of epilepsy and what the subject was actually seeing was their child whose features their brains could not interpret and were understood by the brain to be aliens.
Most of the sightings happened in their homes and often in their children’s bedrooms..
So in conclusion, the sightings were real in the minds of witnesses, but there were no aliens