In public co op, i often experience a bug where i get disconnected with the error lost connection to host. This can be 2 min into the game, or 45 min. There appears to be no lag, everything is fine, then bam.
As there's no option to show ping or packetloss, it's hard to say, but as there's no lag in the game that does not appear to be the cause.
Private co op works perfectly fine, no issues there.

The problem right since there is no chat, or any notification when a host will quit, it is impossible to tell the difference between someone who just close the game or a bug on the host end or an issue in our side.

When the host is clicking to quite a coop session a countdown should show the same as when you switch between region.
That way at least everyone know the host is going to leave and it is not related to a bug.

Hey Raphael, I'm experiencing this too on my ps5, Im playing with my girlfriend my internet is perfect I'm connected via Lan cable and I have a very good internet. But for some reason I'm continuously disconnected ever 5 - 45 minutes my dad doesn't have any issues and he isn't connected to the internet through Lan cable. I've tried unplugging the Lan cable and changing spots on the router but nothing works. Hope I didn't waste 60 dollars.