I was recently moved on an international flight. I had my boarding pass printed with my original seat and had to check in with my passport before my flight and had another seat assigned.
Check-in agent said to ask at gate, so I asked at SkyClub. She couldn't tell.
Asked at gate and gate agent didn't know.
I asked, very nicely, but firmly, for my seat back, and got it.
No explanation given why it was changed and no issues after boarding.