There are three terms to clarify first:
The “bibliography entry” (bib-entry) in the internal or external bibliography database is describing a cited document by Authors, Title, Journal, Number, Year, etc.
The “bibliography index” (bib-index) is typically a list of formatted bibliography entries listing all cited documents in a paper as index.
The “citation”, typically is a sequence number given in the text in brackets “” pointing as crossreference from the text to the particular bib-entry in the bib-index.
If you need to update the bib-entry because something was missing or mistyped, just do it by “bibliography entry” “edit”.
However updating the index will not reflect your change in the index. (This is the bug!!!)
Go into your text where you’ve cited the document in question, insert the “citation” newly (a second time, the citation is now duplicate “” !!!) and remove the old citation (yielding “”). Finally an update on the bib-index will reflect your changed bib-entry in the bib-index.
The same method applies if you are changing entries in an external bib-database and want to have the changes reflect in your bib-index.
OK, this only works for small papers citing only a limited number of bib-entries. There is no solution for big papers or books. The recommendation is to use other tools like Zotero or Mendeley to collect your entries and compile your indices.
(I’m writing this for myself, as I always forget how to fix it.)