I'm having the same issue on my wife's computer. Bought one before, ran into some issues (possibly due to hardware defect) so now we have a replacement. The other issues are resolved, but we ran with Win-Defender for about a week. Just installed Avast, and "eventually" we saw the internet connection was killed after some time (far more than 5 minutes). How do I know it was Avast? Because I disabled it and then the connection came back...
Again, it's not frequent, but it's annoying as hell.
Please don't suggest "clean installs" or whatever, because I have tried those before with no solution. Besides, this is a brand new machine, just a basic minimal install, and nothing else. Again, the machine ran fine for a week or two without Avast, and had no issues... and the day after installing Avast this happens again. Admittedly, our general purpose machine (the one I'm typing this on now) is running fine again... don't know what fixed it on here, but it doesn't have the problem anymore. But, as posted before here
https://forum.avast.com/index.php?topic=222690.msg1480467#msg1480467 it also had a problem.
Sounds to me like Avast is losing it's quality... very disappointing to see...
Any REAL ideas or solutions are welcome.