Raspberry Pi got stuck on "HTTP server listen" message


<date-time> grafana-server[790]: t=<date-time> lvl=info msg="HTTP Server Listen" logger=http.server address= protocol=http subUrl=

My Raspi recently got stuck several times in a day. In /var/log/messages I found that every time the message above is the last message just a moment before stuck.

I use Grafana v.6.2.5 with InfluxDB over Raspi 3B+ Jessie.
I checked the file system and it shows no defects.

What might cause the getting stuck problem?