To reproduce:

• Add a key to an existing group and click Save.

Observation: The changed group listed in the Groups dialog shows the new number of keys.

• Close the Groups dialog.
• Open the Groups dialog.

Observation: The changed group shows the old number of keys, i.e. the change wasn't saved.

In T7181#190402, @ebo wrote:

But when trying to make changes to that group it first looks as if it is possible (I removed half of the 6 certificates and renamed the group) but after closing the group configuration window and opening it again the renaming was still there but it was again 6 certificates in the group.
A new group can be created but again can't be changed persistently.

In T7181#190448, @ebo wrote:

In Debugview I see, after only opening the group configuration dialog:

31	1043.134342	5624	kleopatra.exe	org.kde.pim.kleopatra: GroupsConfigDialog(0x51051f0) loadGroups
32	1043.135916	5624	kleopatra.exe	org.kde.pim.kleopatra: open_or_raise showing window

After opening the group for editing:

33	1074.372279	5624	kleopatra.exe	org.kde.pim.kleopatra: GroupsConfigDialog(0x51051f0) saveGroups
34	1074.374000	5624	kleopatra.exe	org.kde.pim.libkleo: Updating group "neue Testgruppe 1" (id: "hZlZ3oBP", source: 1, keys: 2, isImmutable: false)
35	1074.374099	5624	kleopatra.exe	org.kde.pim.libkleo: writeGroup Writing config group "Group-hZlZ3oBP"
36	1074.374712	5624	kleopatra.exe	org.kde.pim.libkleo: Updating group "test-pgp3" (id: "liXIAFgt", source: 1, keys: 6, isImmutable: false)
37	1074.375772	5624	kleopatra.exe	org.kde.pim.libkleo: writeGroup Writing config group "Group-liXIAFgt"
38	1074.375862	5624	kleopatra.exe	org.kde.pim.kleopatra: onKeysMayHaveChanged ignoring changes caused by ourselves
39	1074.376028	5624	kleopatra.exe	org.kde.pim.kleopatra: GroupsConfigDialog(0x51051f0) loadGroups

And then nothing at all while making the changes and clicking "Save".

In contrast, in an older version where changing the group works, the order is as expected, write is executed after making changes and not before.