I am Bill from Fortinet, and I would like to investigate your issue. 1. Could you please execute the following commands multiple times?
get sys status diagnose sys top-mem 250 diagnose sys scanunit stats all diagnose hardware sysinfo memory diagnose autoupdate versions diagnose debug crashlog read
2. What is your device version? Could you please share the backup configuration along with the output of step (1) to my official email: bhoang@fortinet.com? I will review the logs and attempt to reproduce the issue in my lab to identify the root cause. Thank you