Been experiencing this after I moved to my PS5 from Switch.
Every single time I try to play with friends I get disbanded from squad, also saying that the host couldnt be reached. When in open world area's it seems to be going fine with joining an existing squad, but when I fully load im disbanded. Also experienced this when being in a squad but not doing any missions, after a short time I get disbanded from the squad.
It doesnt seem to be a problem with my friends tho (All PC), and havent experienced this on Switch, so it could be a PS5 issue, but im not sure.
Only way to bypass this and play with friends is joining a mission that has already been started. No disconnects during missions, but im immediadly disbanded automatically after the mission ended.
Also checked any network settings but didnt find anything wrong.
Hopefully a fix for this will come soon