It may or may not have to do with whether you have WAN aggregation turned on (which I do). The first time it nearly bricked, I was luckily able to recover by turning off WAN AGG.
The second time I had to factory reset and downgrade.
If you havent already update to this firmware, you should hold off. This nearly bricked my router twice. ASUS support has been notified but they have not removed the firmware.
If you do install it and your router goes into a boot loop. You will need to hit the factory reset button, setup...