My brother and me bought the game yesterday. Don’t know about this bug. Wrote an email to the support team, but poorly only the classic answer like restart ps5.
Any ideas to fix it without the help of the support?
Everytime he fights, the screen freezes for about 7 seconds, the it goes on for 3 seconds, then another 7 seconds of freeze. After a few attempts the game freezes completely and over an hour of playtime is thrown away. Please help. 
P.S. if support read this, please check my latest mail. Thank you.
It’s horrible and unfortunately not much going on about it.
For your Information: We’ve fixed it so that the image doesn’t completely freeze. In other words, it still stutters a bit, but you can at least finish a game, even during larger battles.
First we removed all internal data from the game on the ps memory. Then we turned the ps5 off and unplugged the power cord for about 30 sec.
After turning it on:
Then go to the home screen and select settings, saved data and game/app setting. Select [Game Preferences].
Instead of “Game Defaults,” select Performance Mode. It helped us a bit. Also, in the AoM settings, select Performance Mode instead of Quality Mode and disable Bloomer. We also disabled game recording.
We’re still waiting for the update, but in the meanwhile, this works for us.
Maybe you can give some feedback, if this works for you…