Hass.io and Mosquitto add-on - works only on 1883 port and plenty of strange messages in the log

I have Hass.io 0.83.2 and Mosquitto add-on installed and configured.
Tried to follow this guide and disable listening to 1883 port, but couldn’t get it running if I remove 1883 port and use any of 1884, 8883 or 8884 in my client’s configs.

Also, can see plenty of suspicious messages in its log:
1544047340: New client connected from 192.168.0.40 as entrance (c0, k60, u’mqtt’).
1544047430: Client entrance has exceeded timeout, disconnecting.
1544047430: Socket error on client entrance, disconnecting.
1544047431: New connection from 192.168.0.40 on port 1883.
[INFO] found mqtt on Home Assistant
1544047433: Client entrance disconnected.
1544047433: New client connected from 192.168.0.40 as entrance (c0, k60, u’mqtt’).
1544047487: Saving in-memory database to /data/mosquitto.db.
1544047583: Client entrance has exceeded timeout, disconnecting.
1544047583: Socket error on client entrance, disconnecting.
1544047584: New connection from 192.168.0.40 on port 1883.
[INFO] found mqtt on Home Assistant
1544047585: Client entrance disconnected.
1544047585: New client connected from 192.168.0.40 as entrance (c0, k60, u’mqtt’).

entrance is a tablet with WallPanel running. I can see its status messages using mosquitto_sub

So what are these errors about and why it’s impossible to use ports other than 1883, any ideas?