Review Changes button doesn't do anything

I have a .bib file which I have modified and wish to save. Every time I try to save it, I see a dialog “File updated externally” with buttons “Review changes”, “Save” and “Cancel”.

When I click “Review changes”, nothing happens. I believe this feature was working prior to Jabref 4.1, but perhaps something has become broken in this or some recent version update.

JabRef 4.1
Windows 7 6.1 x86
Java 1.8.0_161

I think this issue is already fixed in the latest development version (which will be released as 4.2 in a few days). If not, then please report a bug at github. Thanks!