Ideal behavior:
# Create a citation; use page= or quote= to make the citation specific to a particular part of an article (something like "X said Y <ref>page 111 shows where X said Y</ref>
# Write more text ("later X said Z"); select the citation menu and "Re-use"
# Have the option to add a different quote or different page number showing where X said Z
Instead, and I think somewhat confusingly to new users and not-usefully for power users, editing page= or quote= will also change the page number and citation in the previous citation.
You can see an example of where this would be useful [[ https://en.wikipedia.org/w/index.php?title=Barry_Lyndon&diff=657205320&oldid=657131167 | here ]] where I have created two cites that are redundant because the original cite included a quote that I wanted to retain but wasn't appropriate for the next citation to the same book.
As far as I know, doing this the Right Way would also require changes to the underlying reference/citation system, so this may not be a VE bug per se and could even be a WONTFIX, but filing it for completeness.