Some websites get ERR_TIMED_OUT

Hello

I have been looking for this problem for a while now.

Support was useless.

On 2 different sites, at random moments, some websites are returning ERR_TIMED_OUT .

Site https://www.bankinter.com/ or another one point on a server on Azure.

I know they work because on the third site with Ubiquiti or from home, it works.

I have : 

1. pretty much any filtering from Firewall rules

2. checked and changed the DNS

3. upgraded to 19.5MR1

4. Disabled HA (no matter if it is disabled / A/P or A/A)

5. changed the internet connection

I already have a post about this but never really got help.

This is my last attempt before I ditch these Sophos.

Any clue is appreciated.

Don't hesitate to ask for screens or logs, I can provide.

Thanks

Fab