in my logfile I find the message
1554114044: mosquitto version 1.4.10 terminating
1554114062: mosquitto version 1.4.10 (build date Wed, 13 Feb 2019 00:45:38 +0000) starting
1554114062: Config loaded from /etc/mosquitto/mosquitto.conf.
1554114062: Opening ipv4 listen socket on port 1883.
1554114062: Opening ipv6 listen socket on port 1883.
1554114082: New connection from 192.168.178.116 on port 1883.
1554114082: New client connected from 192.168.178.116 as DVES_3B7769 (c1, k15, u'DVES_USER').
1554114116: New connection from 127.0.0.1 on port 1883.
1554114116: New client connected from 127.0.0.1 as paho48699998613 (c1, k60).
1554115873: Saving in-memory database to /var/lib/mosquitto/mosquitto.db.
1554117674: Saving in-memory database to /var/lib/mosquitto/mosquitto.db.
1554119475: Saving in-memory database to /var/lib/mosquitto/mosquitto.db.
1554121276: Saving in-memory database to /var/lib/mosquitto/mosquitto.db.
1554123077: Saving in-memory database to /var/lib/mosquitto/mosquitto.db.
1554123361: New connection from 192.168.178.116 on port 1883.
1554123361: New client connected from 192.168.178.116 as DVES_3B7769 (c1, k15, u'DVES_USER').
1554123695: New connection from 192.168.178.116 on port 1883.
the 192.168.178.116 is the ip adress of my Sonoff_Pow switch.
the 127.0.0.1 is the adress localhost.
In my config I work with two server, one is the pimatic and the other one is openhab2.
Both config connect to the mosquitto and there to the Sonoff_Pow switch.
In your logfile you can read the disconnecting
1554363963: New connection from 127.0.0.1 on port 1883.
1554363973: Client <unknown> has exceeded timeout, disconnecting.
1554363973: Socket error on client <unknown>, disconnecting.
so if you do not have additional mqtt clients in your enviroment than does it mean that there is something wrong with you pimatic-client.
Also this line says it to me.
1554363866: Socket error on client pimatic_0cecf3cc, disconnecting.
perhaps you change your config in pimatic in the way like mine config file.
“host”: “192.168.178.42”, -> here for you localhost
“port”: 1883,
“keepalive”: 180
Is the only difference I can see.
LG Manfred