After some investigation we found that it's not actually the driver or root drivers to blame. It's Microsoft's new policy that was put in effect after one of Windows updates. Now they require additional verification in their Dev Center (us as a vendor).
We went through all the necessary procedures and the changes we submitted are currently pending.
Just wanted to say that indeed there is a problem with viewer 6.8 just as you describe. We are currently investigating it and testing different solutions.
Since it's a problem on the Viewer side the Host logs won't help us much. They can only confirm that the problem at hand is not the Host's, but the Viewer's.
But you can still help us figure out this problem if you send us the Viewer log (use support@). The log should preferably capture the moment when the connection is going offline/online. Along with the log, please, also send us your license key (even if it's a free license key) - this will help us properly identify the connection in our server logs.
The log looks ok - it seems that the Host successfully establishes connection to your server and is ready for connection.
I'm afraid that the connectivity (network) issue might be on the Viewer side. You should check if the Viewer PC can communicate with the server PC and if the connection is stable (you can try the ping -t command, for example).