An easier solution to this problem with FindAGrave citations is, in my opinion, to add the FindAGrave external link template to the end of the citation, then to copy/paste the memorial number into the template.
Here is the template format that I use:
{{FindAGrave|NUMBER|sameas=yes}}
Replace the word NUMBER with the memorial link.
If you link to a different person's memorial, replace the word yes with the word no.
My understanding is that some browsers (such as Firefox which I use) do not copy all the links in the citations on the FindAGrave memorials. Adding the template to the citation gives us an easy way to provide the missing link (intentional pun!).
edit: Made some edits for better clarity.