No real update from my end but when trying this morning I now find my UK home address pre-populated in the address section of where I am staying in the US. Secondly when hitting save, despite getting the opaque error message, I still get an email saying contact details have been updated. What matters to me most is getting my Redress number on the booking - without that I will no doubt have a SSSS at LHR and painful CBP interview at JFK in the evening when I land (thankfully no connection until the next morning just some lost sleep) - irritating though not entirely surprising that BA could have not made such a critical field separate (and therefore remains intact) from the rest of their comedy error-prone API interface.