Something similar recently happened to me. In Sept I booked for July 2025 DUB-FAO and bagged 4HK and 5K. My wife and I and my 10 year old daughter. About 2 weeks later I got an email from EI that stated due to operational reasons my seat assignments were now 7K, 2A and 3D. I phoned the Concierge line and they said it was a computer generated change. Unfortunately our original seats were gone so we were put in 3DGK. Aer Lingus couldn’t explain why the changes occurred and had a couldn’t care less attitude in dealing with me.