I posted yesterday on this and the post has 'gone' in the back-up restore, so here goes again!
This may or may not be associated with the issue but certainly reflects some database corruption. It is still the case in the current post-restore position.
G-STBD, B777-36NER is cn 38695 line no 968
However, it is showing in the database as cn 40542 but with 'also registered as' a whole raft of other B777s. 40542 is G-STBA which is amongst the duff data set.
Over to the experts!
Pete