Guest goes offline for unattended connection, become stable if machine is access remotely V 20.10.957.7556

Typically in the past when I've seen behavior like this it's caused by a firewall/AV/application that is monitoring keep-alive connections and occasionally shutting them down or interfering with them.

Do you have other machines at this location with the same problem?

There are a few more machines in different locations with the same issue, I could check a few of them and they are using LTE connection.

Normally the network is: PC -> router -> Lan or WIFI or LTE modem, the PC we use is a NUC intel and the router is the Mikrotik. and for the LTE is the Cradlepoint devices, for the WIFI we just change the config on the router.