I would add that Player 2 also disconnects when we travel together on a raft and coming close to an island. The island is completely empty. After a while Player 2 disconnects and the island finally loads.
Besides of that I can’t name a specific moment because it just happens all of the time without a particular reason.
We both use a PS4 with Wifi connection. We live in separate households. Also we’re using the recent version of the game. Our NAT Type is moderate. We live both in EU but also tried using “Auto” as a region. At the moment we played around 30 days but the issue appears since day 10 I guess. Our islands are not customized.