ZIA crashing randomly with SIGTERM received

I’m running ZCC under Linux Mint 20.3 (Ubuntu 20.04). The installation procedure completed without error. I can establish a connection and login to our service. At random times, normally around 30 minutes after logging in, zstunnel crashes with a message “ERR Interrupt signal (15) received!!!” in the log files. All connections are shut down and generally I have to reboot the machine. I can send the log files if required.

Thanks in advance.