never heard about that... - try to clear log ----> rm .config/scorpius/yappari.log start yappari, open a private chat window and try to have a conversation when you are sure your friend should have sent you messages, close yappari and post here yappari.log to let devs have a look...
INDEX DATA XXXXXXXXXXX@s.whatsapp.net Contact There's no previous chat window Initializing logger for XXXXXXXXXXX@s.whatsapp.net Logger for XXXXXXXXXXX@s.whatsapp.net initialized successfully. LastId: 2 Reading log for XXXXXXXXXXX@s.whatsapp.net... Log retrieved in 4 milliseconds. Created chat window for XXXXXXXXXXX@s.whatsapp.net ID: 58720305 Showing chat window Chat window showed 201 milliseconds. OUTGOING: <iq> id=last_4 to=XXXXXXXXXXX@s.whatsapp.net type=get <query> xmlns=jabber:iq:last Setting chat window title Window title set createChatWindow(): finished INCOMING: <presence> from=XXXXXXXXXXX@s.whatsapp.net Updating contact XXXXXXXXXXX@s.whatsapp.net INCOMING: <chatstate> from=34642523095-1432364332@g.us participant=34642864184@s.whatsapp.net <composing> INCOMING: <iq> from=XXXXXXXXXXX@s.whatsapp.net id=last_4 type=error <error> code=501 text=feature-not-implemented OUTGOING: <chatstate> to=XXXXXXXXXXX@s.whatsapp.net <composing> media=undefined xmlns=http://jabber.org/protocol/chatstates OUTGOING: <chatstate> to=XXXXXXXXXXX@s.whatsapp.net <paused> xmlns=http://jabber.org/protocol/chatstates logMessage(): Message ID 1438265380-2 OUTGOING: <message> id=1438265380-2 to=XXXXXXXXXXX@s.whatsapp.net type=text <body> Hi Chat for XXXXXXXXXXX@s.whatsapp.net found. logMessage(): UPDATING receipts logMessage(): INCOMING: <ack> class=message from=XXXXXXXXXXX@s.whatsapp.net id=1438265380-2 t=1438265637 Chat for XXXXXXXXXXX@s.whatsapp.net found. logMessage(): UPDATING receipts logMessage(): INCOMING: <chatstate> from=XXXXXXXXXXX@s.whatsapp.net <composing> INCOMING: <chatstate> from=XXXXXXXXXXX@s.whatsapp.net <composing> Closing outstanding notifications for XXXXXXXXXXX@s.whatsapp.net User has quit the application Application destroyed