If anyone is having problems with their points from Sainsburys I think this may not be a fault but a flaw in the system. You need to remember BA uses Avios and Sainsburys uses Nector. From what I can see online you have to manually redeem your Nectar points into Avios. It would be best to log in to your Sainsbury account and check all your loyalty points have been gained. Then go into the Avois and manually convert them in small batches to make sure they all migrate across without getting lost.