Join Date: May 2012
Location: Munich, Algarve, Sussex or S.F Bay Area
Programs: Mucci, BA Gold, A3*Gold, AA Plat, HH Gold, IHG Plat Amb, Marriott Plat
Posts: 4,163
That happened to me many moons ago and BA claimed it was not possible if it was part of the same booking. It was a minimal amount of Avios in my case, so I didn't bother pursuing it. I remember thinking it was BS when told.
When it was about to happen to Mrs Tafflyer, we deliberately removed her BAEC number from the final flight of the booking. After the status upgrade, we retro-claimed the flight which was processed with her new status. Self help against BA IT.