Hey, first of all congrats on digging deep and getting FF done ( again)!
All the comments and advice are spot on. So many factors can play a role with one aspect of a test. Already mentioned was -Hydration, both prior to and during FF. How was the environment of your pain cave, was it hot, humid? Did you have adequate ventilation? Another mention was fueling prior to the test. Have you made any recent dietary changes? Don’t beat yourself up about it, it happens to all of us. The good news is your increase in FTP and MAP. Your AC could be an anomaly. Try doing the suggested rides to improve your weakness, like The Omnium, The Shovel, The Downward Spiral, and The Cure (not all in a row😆) If they feel easy(ish), bump your AC up 5%. Hang in there and keep up the good work!