first rule of the fight club........ don't talk about it too much nor call BA to point out the error.

we know that BA's IT systems aren't great and there are various (borderline predictable) glitches in all sorts of departments including TPs.

much guess / suggestion would be that if it hadnt bee corrected within a few days of the flight, it's unlikely that any correction will take place on the day your year resets.

even if that happened, I think it would be reasonable for you to then have a conversation with BAEC and explain that you had worked on the assumption that what was being displayed was correct and that you'd hit the threshold.

if you are loosing sleep over it, take an extra flight to be completely safe but I think you'll fine.

don't forget, fight club.....