Did you find what was wrong with the EFOB because I tried it yesterday and changed the FL, up two positions for a total of 4,000 feet, and all was fine but the top of descent never showed and I just had to wing it, so to speak.
I updated things yesterday in MSFS 2020 and was flying the A350 from TNCM to PANC and all was fine, but then I encountered EFOB errors and half way in the flight it went up to 15 .4. Later, I tried a much shorter flight and all was fine.