Sophos UTM is stopping working by sudden

Hi, good morning.

For 2 days in a row, I arrived in the office and we had no Internet. Both days I rebooted Sophos UTM and then the Internet was back.

Yesterday I thought it was an AT&T issue, because we lost the internet at the same time as AT&T had issues on their end.

Now, checking further, I see we have no logs since 2019-12-04. No changes were made in the settings recently. We have no logs for any module for the past 2 days.

Checking the graphs, there are nothing during these down time. Please see below:

Even the CPU and RAM usage has nothing to show:

Again, there were made no changes recently. Actually, the last change dates from 2019-11-20 (pattern added to the Antispam filter).

Have someone already seen this before? Any idea of what is going on?

Thanks!

EDIT:

By the way, we have Sophos UTM 9, running the firmware 9.605-1 (I scheduled the update to the 9.700-5 version for later today)