A "commenters" at the vid link suggests reflections of a passing car or truck. Looking at it, it seems to me the comment is written more for deflection.
These window flashes come at a time when a crane is videod taking or putting something on the roof, and the concrete circle around not just the fountain, but most of the front lawn.
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How despicable that we, the people, don’t know what the heck is going on with OUR house, the White House. Dolly Madison would be furious.