Are you sure you are on the latest firmware? The latest is 073.040.086.15410.
Since it appears to be a DNS issue, just set the DNS to static, make the Primary DNS the same IP as your gateway(router) and set the secondary as 8.8.8.8.
There certainly is no issue with Connectkey firmware that has occurred since 2014 so it is either the weirdest hardware failure in a network controller I've come across, or something odd in your setup.
On my 7845 networking dies in a funny way:
local access to the web interface is alive, but connectivity to the Internet dies after some time (randomly, from hours to days), restarting the machine helps, also restarting the network interface helps...
The result is that we cannot scan to email or scan to the cloud unless we restart the interface on a daily basis....
Newest firmware (however this problem was there with the 2014 firmware too), tried restoring to the factory settings too - it did not help.
Please help me with this.