We have the exact same issues, my husband and I. Interaction with Raphael was a white screen. Interactions with guardians were horrid, one was muted and they both happened at the same time.
I wish there was a way to delay the interaction for one player so the other can at least get the same experience.
The game is acting as if we're having two different playthroughs instead of being a team! We can't interact with each other at all, everything is happening separately, we can't interact with each other's followers... This is a far cry from DOS 1 and 2, I can't understand why they did things this way.
I think you can ask for a refund in PS5 store, you should have a 2 weeks time frame to do so, but I don't know how to access it. Probably on PC instead of on PS.
We won't ask for a refund, but I completely understand that other people would want to. We hope Larian will fix things in near future - I am positive that they are aware of these problems with split screen on PS5, there are just too many of us reporting these exact same issues. What I can't understand is why they are not acknowledging this publicly, so we could at least know what exactly is wrong and how they are working to fix it.