FortiGate randomly drops VPN connections without any clear reason

Hi all,

I’m facing a frustrating issue with my FortiGate firewall. Remote users are getting disconnected from the VPN randomly throughout the day. There’s no pattern to when it happens sometimes within 10 minutes, sometimes after an hour and the users have to reconnect manually each time.

We’re using SSL VPN, and everything looks fine in the logs. Bandwidth is stable, and there are no clear errors reported when the connection drops. The same users are reporting it across different ISPs and devices, so I don’t think it’s just on their end.

I’ve checked timeout settings and session TTLs, and nothing seems off. At this point, I’m just looking for any angle — even reviewing small details like session behavior, logging anomalies, or traffic patterns. Sometimes, looking at the issue through a fresh lens (like categorizing by nouns that start with A — activity, authentication, allocation) helps uncover something you’ve overlooked.

Thanks in advance for any help.