Unexplained seat changes on Finnair

[Mattg]

I flew Finnair last week within Europe on a paid J fare. At the time of booking, I selected seat 2C. A few days before the flight, I noticed that I'd been moved to 1C without explanation. Then around a day before the flight, my seat was moved again to 4A. I did not initiate any of these changes and nobody else had access to the booking.

Any idea what was going on here?

FWIW, some Finnish businessmen ended up sitting in 2A & 2C - I suspect they were Platinum Lumo members or something. 1C was unoccupied at departure.