As described in https://xmpp.org/extensions/attic/xep-0384-0.3.0.html#usecases-keysend, if transport key message is received, it is reported in the client as message not encrypted for this device.
The issue should be fixed now. It needs to be verified in the future build of BeagleIM/SiskinIM.
As described in https://xmpp.org/extensions/attic/xep-0384-0.3.0.html#usecases-keysend, if transport key message is received, it is reported in the client as message not encrypted for this device.