I am more than 160 hours into AC Odyssey on a base PS4, finished the main game and the Legacy DLC. Apart from minor bugs here and there, the game ran perfectly fine up until now. I've started Fate of Atlantis and reached the Elysium map, and the game's suddenly riddled with severe technical issues. It freezes constantly when riding a horse or sailing the ship, the framerate drops to like 10 fps or less during intensive action, and I get constant texture pop-ins and loading issues, stuttering, and flimmering. It's getting to the point where it's nearly unplayable and I don't wanna continue under these issues.
My question is, is this common with the Atlantis DLC or particularly the Elysium map? Is there any way to fix it? Or is it more likely a problem with the console, e.g. a failing HDD or something? I already rebuilt the database in safe mode, the PS4 runs well otherwise.
Thanks in advance for any suggestions.