I now tried the latest version 3.5.0, but still the same behavior. ZS reboots every 2-16 hours.
Since a few days I again try to debug the crashes with the help of log files and all I can find on the issue on google. It looks that in the moment of the crash the kernel can’t do anything more but reboot. No entries in log files, no crash dumps, no messages or any data on SSH connection (for example dmesg outputs).
SSH connections are not closed by ZS in the moment of crash. When I try to use the SSH terminal after the crash it seems to be still connected, and it comes with the message “pipe broken”.
I have some experience with linux systems. I never encountered a behavior like this before. Crashes of Linux are very rare and I never encountered a crash without any hints in log files or on the screen just like pushing the reset button. If I had to guess I would assume a hardware failure of the PC. But when I boot the system again with the 3.2.1 version, everythings is perfect again.
For my needs, ZS is best router distribution available (thank you Fulvio for your work). I also want to benefit from secrity issue fixes so I would be really glad if someone could help me with this.