Drag/drop doesn't work via SSH (Dock tab, Display editor, ...) with GTK3 on Linux

[kasemir]

Dragging tab panes around between windows doesn't work when working on a remote Linux system via ssh.
Tabs can be dragged, but instead of dropping in the desired location, a new window is created because the drag-over and drop events are not received.

[kasemir]

Drag/drop works when using -Djdk.gtk.version=2, and fails with -Djdk.gtk.version=3.
Details may depend on setup of computers used on server and client.
In the tested case both are RHEL 7.5.