Two burials/memorials?

[Kit]

findmypast had some new Scottish memorial transcriptions released recently. I was having a look to see if we got images or just transcriptions and found a memorial for my 4g grandfather James Crawford.

I then googled to see if I could find an image of the memorial elsewhere, which I failed to do. However, I did find a find-a-grave memorial for the same James at a different cemetery, which triggered a memory of a distant connection saying there was a family vault or something on an island, a place I would not have looked.

Can anyone think of a reason there would be 2 grave type things for 1 person?

Attached are the pages, if anyone wants to look.

FMP

Findagrave

FMP mentions a daughter Sarah I have never heard of and can't find a baptism for. I've found her likely death on Scotland's People in 1818.