JabRef 4.0, 4.1 and 4.2 freeze on High Sierra

I have tried to upgrade to JabRef 4.0, then 4.1 (then even dev 4.2) on MacOs High Sierra.
Each time I import a new article, it’s fine at first, then any following action will freeze.
As recommended on one similar post, I have changed my /etc/hosts file adding my localhost, but it’s not better.
I have java Version 8 Update 161.
It’s so frustrating that I have downgraded back to my old JabRef 3.8.2…
(I had to fetch my old version of the .bib file though, because all my groups had disappeared from the new .bib, when upgrading to 4.1… more frustration).
Thanks for any help.

as we recently discovered there might be an old version of JabRef which shipped with an older version of java that does not get removed completely.

You first have to uninstall any old JabRef version before installing the latest version.

Pleas report back if that works