>1. In Device Manager, check the properties of the adapter and make sure the computer is NOT allowed to power down the adapter to save battery. If you leave your laptop inactive for long enough that power saving settings kick in, this might be the cause.

I am working on it when it happens. Also, this is plugged to AC.

>2. At a client site you're probably getting an IP address via DHCP. Normal DHCP lease time is 24 hours. I've never seen it less than that but it is possible to set it higher or lower at the DHCP server. You might ask if anything like that has been done.

Ok

>3. Some hosts can only accept a certain number of connections e.g. a Windows workstation 10 simultaneous connections. If you're connecting to something like that and you're the 9th or 10th connection you may find it unreliable and/or you may be disconnected from time to time.

This is not the case here.

>4. Some networking devices such as Cisco ASAs also may be limited in the number of connections they are licensed to allow

This is not the case here.