That's actually a catch 22 of sorts. The funny thing about the brain is that (and this neuroscience has proven) the brain treats memries as real, ACTIVE events. Not just treating them as things that have happened, but as if they are actively happening in the present (hence, when you're "living in your past" you're literally doing exactly that). Dreams are almost a secondary version of that. Our bodies treat dreams as something akin to an actual event, though without the physical reprocussions. In fact, much of that is because our dreams are built from our memories and perceptions. So if our dreams are built on memories, our brain treats them like they're really happening. And if we remember them later, we're actively reliving them AS memories. Following logic, "If A=B, and if B=C, then A=C" -- if our dreams are memories, and if memories are treated as active events, then our dreams are treated as active events.

If you're getting actual flashes of memory images, then what you're describing sounds to be closer to PTSD than de ja vu. They sound like flashbacks, to be blunt. And if they are (you notice I didn't say anything about mental repercussions of dreams) it is conceivable that this recurring dream has ingrained itself to the point that you're literally reliving it every so often now in waking life as a flashback.