I looked at those and I think there were only two flights. There was another Piper (532MJ) about the same time. My guess is somebody made an error filing two flight plans for two planes. I see alot of planes out of one FBO here where they show up on FA as a Citation when they are really a 210, etc… They probably use the same computer in the lobby of the FBO.
Could these be part of a school? The Central Washington Univ flight dept makes alot of IFR training flights here. Their planes are actually operated through an FBO and they have a variety of registrations.
I once has a N96575 and a N46575 (both C172s) on frequency at a time, another time three Sky Arrows: N384SA, N454SA and N455SA. Lastly, not as bad, I had N562AG and N562AD (both C172s),