What's the basis for déjà vu?

Like many people I occasionally experience déjà vu. It's very disconcerting, like you momentarily become lucid enough to realize that you're living in a temporal loop. 

There are "scientific" proposals, which attribute it to a kind of brain misfiring. Perhaps that's correct, but to my knowledge it's just speculation, and speculation based on physicalism. There's no hard science to back up that explanation. 

I have my own conjecture, which may or may not be correct. Perhaps déjà vu is like a momentary out-of-body experience where the mind and the brain become unaligned for a few instants. 

There's also the way we normally process time, but there are situations where that can change radically. Take mountain-climbers who fall but survive. During the interval between falling and landing, the mind processes time at a different rate and they see a rerun of their lives. 

That's one of the mysteries of knowing what time is really like. We're normally so immersed in the temporal process and conditioned by the temporal process that we lack the detachment to analyze it objectively. But there are situations where the way the mind, filtered through the brain, normally processes time, breaks down. In that altered state of consciousness, the perception of time's linearity or uniformity is disrupted. That's disorienting. It's possible that if we continued in that state we'd adjust, sort in out, and experience the psychological passage of time from a different perspective.