Just updated to JabRef 4.0 on two Macs (iMac and Macbook Pro), both running High Sierra. Choosing Quit from the File menu closes the window, but the app does not in fact quit. The only way to exit appears to be force quitting the program. The problem occurs on both machines.
This seems to be a bug. Can you please report it at https://github.com/JabRef/jabref/issues/. Thanks!
Just did that, thanks.
I am having the same issue.
please try again with the latest snapshot http://builds.jabref.org/master/
(For mac you have to download it via wget, otherwise the application is marked as damaged)
Thank you Christoph; I did have that issue with the damaged file.