Bei mir war einer unter dem Hotel in dem Schacht. Hänge bei 4/5, aber der letzte ist an keinem der Screenshots Plätzen aus dem Guide. Frustrierend...

Found this Threads
https://psteamcommunity.yuanyoumao.com/app/2183670/discussions/0/600785827026655858/

I think two locations have been changed.
They are the third and fourth locations in the guide image.
One is under the basement bedroom,
and the other is near the bridge to the agricultural island.

I may not be explaining this well in English. I apologize, as English is not my strong suit.

all 5 stones on first island, 1 near port 2 cave 3 under Trees 4 fountane and if u build bridge to new island, behind him from left (it hard to spot behind texture bridge). if not ,in same place.

yeah, I am missing the last one too. It's probably somewhere behind the rock...
Devs should make it visible all the time, otherwise it's just confusing...

I'm gonna share the solution to this quest created by one fo the players so you can find all of the pieces.
1. By the grave lake to the left.
2. In the forest between grave and hotel, closer to the grave but right at the "frontal edge" of the island.
3. in a tree trunk right from the hotel in the background.
4. By the lake close to that 3rd piece in the background.
5. At the harbor move your screen a bit right and down and find it on one of the stones, close to the left edge of the island

lol, found it. It was hidden behind the bridge!!