smack request might be not acknowledged (resulting in connection termination)

Sometimes smack requests are not acknowledged. Like here:
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10/10/2017 13:07:01 (I) nbxmpp.client_nb raising event from transport: :::::DATA RECEIVED::::
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<a h='38' xmlns='urn:xmpp:sm:2'/>
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10/10/2017 13:07:01 (D) nbxmpp.smacks Got ack for outgoing stanzas (our h: 74, server h: 38), removing 1 messages from queue...
10/10/2017 13:07:01 (I) nbxmpp.transports_nb pollin called, state == CONNECTED
10/10/2017 13:07:01 (I) nbxmpp.client_nb raising event from transport: :::::DATA RECEIVED::::
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<a h='39' xmlns='urn:xmpp:sm:2'/>
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10/10/2017 13:07:01 (D) nbxmpp.smacks Got ack for outgoing stanzas (our h: 74, server h: 39), removing 1 messages from queue...
10/10/2017 13:07:01 (I) nbxmpp.transports_nb pollin called, state == CONNECTED
10/10/2017 13:07:01 (I) nbxmpp.client_nb raising event from transport: :::::DATA RECEIVED::::
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<r xmlns='urn:xmpp:sm:2'/>
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10/10/2017 13:07:01 (I) nbxmpp.transports_nb Plugging fd 19, W:True, R:True
10/10/2017 13:07:01 (I) nbxmpp.transports_nb pollin called, state == CONNECTED
10/10/2017 13:07:01 (I) nbxmpp.client_nb raising event from transport: :::::DATA RECEIVED::::
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...

[ much more only DATA RECEIVED ]

...

10/10/2017 13:07:02 (I) nbxmpp.transports_nb pollout called, state == CONNECTED
10/10/2017 13:07:02 (I) nbxmpp.transports_nb Plugging fd 19, W:True, R:True
10/10/2017 13:07:02 (I) nbxmpp.client_nb raising event from transport: :::::DATA SENT::::
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<r xmlns="urn:xmpp:sm:2" />
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10/10/2017 13:07:02 (I) nbxmpp.transports_nb pollout called, state == CONNECTED
10/10/2017 13:07:02 (I) nbxmpp.transports_nb Plugging fd 19, W:True, R:True
10/10/2017 13:07:02 (I) nbxmpp.client_nb raising event from transport: :::::DATA SENT::::
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<iq xmlns="jabber:client" to="chat@dino.im/NICKNAME" type="get" id="199bc810-39f9-4146-9804-4bd2c95f8901"><query xmlns="http://jabber.org/protocol/disco#info" /></iq>
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...

[ much more similar DATA SENT mixed with DATA RECEIVED ]

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10/10/2017 13:07:04 (I) nbxmpp.transports_nb pollin called, state == CONNECTED
10/10/2017 13:07:04 (I) nbxmpp.client_nb raising event from transport: :::::DATA RECEIVED::::
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<stream:error><policy-violation xmlns='urn:ietf:params:xml:ns:xmpp-streams'/><text xml:lang='en' xmlns='urn:ietf:params:xml:ns:xmpp-streams'>Too many unacked stanzas</text></stream:error>
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10/10/2017 13:07:04 (W) nbxmpp.dispatcher_nb Unknown stanza: error
10/10/2017 13:07:04 (I) nbxmpp.transports_nb pollin called, state == CONNECTED
10/10/2017 13:07:04 (I) nbxmpp.client_nb raising event from transport: :::::DATA RECEIVED::::
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</stream:stream>
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10/10/2017 13:07:04 (I) nbxmpp.client_nb Disconnecting NBClient: policy-violation
10/10/2017 13:07:04 (I) nbxmpp.transports_nb Error while disconnecting socket: Transport endpoint is not connected
10/10/2017 13:07:04 (D) nbxmpp.client_nb Client disconnected..
10/10/2017 13:07:04 (D) nbxmpp.client_nb Calling disconnect handler <bound method Connection._disconnectedReconnCB of <common.connection.Connection object at 0x7f9265999950>>
10/10/2017 13:07:04 (I) gajim.c.connection disconnectedReconnCB called
10/10/2017 13:07:04 (I) gajim.c.connection Reconnect to jabber.ccc.de in 15s
10/10/2017 13:07:04 (I) nbxmpp.transports_nb pollend called, state == DISCONNECTED
This is on a normal bandwidth network. On a low bandwidth network the stream termination message has no chance to arrive at all and the connection breaks with OpenSSL error ECONNRESET.