I have a sheet with two external links. One is local and always works, the other is remote and may occasionally time out.[*] When Calc fails to fetch the remote external link, it also doesn't fetch the localhost link. Instead, I see "The link could not be updated." [*]: I can access the remote link in Firefox, but it does take ~20 seconds to receive a response to the HTTP request.
Actually that was an odd environment state masking a different issue - bug 149427.