Hello. Read the whole topic. My Z9 also works for many hours on the developer firmware. And it happens mostly at night, when I can not control it. My Z9 works on Flypool. But many people have different pools and everywhere the same problem. This problem is not in the pool and not in the miners, this problem is in the wonderful firmware !!! As soon as I reflashed my z9 on Antminer-Z9-DEFAULT-500-DUAL-MODE-201808280957-unlocked.tar everything worked just perfect! The hashrate curve on the pool has turned into a straight line at the level of 60 K/sol. Good luck to all.