JabRef 5.0-dev--snapshot--2019-03-30--master--40600b354
Windows 7 6.1 amd64
Java 1.8.0_201

• [+] I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

Selecting a group shows some entries. Select one entry and then right clicking the group opens among others "Remove selected entries from group". Upon Clicking that line nothing changes, there is a saving but without any effect: the entry count in the group is not changed. The entry stays in the maintable. And changing to another group and going back the entry is still there. The group is not removed from the group field. This is troublesome. That means there is no way to remove from group now, since the right click menu of entries no longer presents the group selection/removal.
Steps to reproduce the behavior:

1. select a group
2. select an entry
3. right click on the group and select "remove selected entries from group"

Paste an excerpt of your log file here