Time by time Mosquitto broker restart on Ubuntu Linux with 2.0.17 and 2.0.18 version

[nagyattila69]

Hi Team,
we have an ubuntu linux server based mosquitto broker communication center in our IoT device management system. Approx 14-15K device connected to this every day and transfer approx. 300K-400K messages. Persistency database approx 250 MB permanently.
When I made the last upgrade of the mosquitto broker from 2.0.14 version to 2.0.17 the system started to make 4-5 times / day a suddenly stop and within some second restart. After 2-3 days it crashed the database so we need to delete and we upgrade yesterday to 2.0.18 version. In the last 24 hours only one time happened this quick restart (what never ever happened before!).

The terminating and start looks like this.
1695190114: Client 7W61821817001000 already connected, closing old connection. 1695190114: New client connected from 213.162.73.81:7852 as 7W61821817001000 (p2, c1, k1023, u'nodecon'). 1695190114: New connection from 46.125.249.22:16932 on port 1883. 1695190114: New client connected from 46.125.249.22:16932 as 7W61821206001100 (p2, c1, k1023, u'nodecon'). **1695190115: mosquitto version 2.0.18 terminating 1695190115: Saving in-memory database to /var/lib/mosquitto//mosquitto.db. 1695190115: mosquitto version 2.0.18 starting** 1695190115: Config loaded from /etc/mosquitto/mosquitto.conf. 1695190115: Warning: File /etc/mosquitto/passwd has world readable permissions. Future versions will refuse to load this file. To fix this, use chmod 0700 /etc/mosquitto/passwd. 1695190115: Warning: File /etc/mosquitto/passwd owner is not mosquitto. Future versions will refuse to load this file.To fix this, use chown mosquitto /etc/mosquitto/passwd. 1695190115: Warning: File /etc/mosquitto/passwd group is not mosquitto. Future versions will refuse to load this file. 1695190115: Opening ipv4 listen socket on port 1883. 1695190115: Opening ipv6 listen socket on port 1883. 1695190115: Opening ipv4 listen socket on port 8884. 1695190115: Opening ipv6 listen socket on port 8884. 1695190115: mosquitto version 2.0.18 running
How can I get more information what is the reason of this type of restart? (storage and memory 80% is free)
What can be the reason of this?
What should I do to find the problem?

Thanks for any help!
Regards,
Attila