Search & Replace character || problem

I have the latest version of Calibre.
I'm trying to correct a problem in an epub format ebook.
Whoever created it managed to replace closing quotation marks (") with double bars (||).
When I click on the "wizard" icon I see the same || characters in the output code.

I'd like to replace || with " but all attempts to do so have resulted in placing " after every single character! "L"i"k"e" "t"h"i"s"."

I'm clearly missing a trick here. Do I need to add an "escape" character, perhaps?

Thanks in advance for any help.